CI: use BuildJet & self-hosted Windows runners

1. Use buildjet for the longer Linux CI workflows.
2. Use a self-hosted Windows runner.
3. Make CIFuzz run on merge to main or release branch.

Two runs each of the original workflow files and the updated
workflows in this PR:

                                GitHub  GitHub   BuildJet BuildJet
codeql-analysis.yml             4m 30s  cached    2m 56s  2m 59s
cross-darwin.yml                3m 10s  3m 19s    1m 33s  1m 30s
cross-freebsd.yml               3m 33s  3m 10s    1m 28s  1m 22s
cross-openbsd.yml               3m 4s   2m 36s    1m 29s  1m 22s
cross-wasm.yml                  1m 59s  2m  2s    1m 12s  1m 16s
cross-windows.yml               2m 45s  3m  0s    1m 44s  1m 25s
linux32.yml                     4m 27s  4m  0s    1m 55s  2m  8s
linux-race.yml                  3m 54s  4m  7s    2m 22s  2m 12s
linux.yml                       4m 23s  4m 39s    2m 37s  2m 15s
static-analysis.yml
 /vet                           1m 41s  2m 22s       52s     56s
 /staticcheck(linux, amd64)     2m 47s  2m 38s    1m  7s  1m 10s
 /staticcheck(windows, amd64)   2m 5s   2m  4s    1m  6s  1m  8s
 /staticcheck(darwin, amd64)    2m 14s  2m 20s    1m 10s  1m 10s
 /staticcheck(windows, 386)     2m 36s  1m 58s    1m 23s  1m  8s
vm.yml                          1m 30s  1m 32s    2m 31s  2m 23s
windows.yml                     6m 23s  6m 19s    3m 40s  3m 53s

A few very short workflows are being left on GitHub-hosted runners, like
licenses and gofmt. These benefit from the quicker dispatch to GitHub
hosted runners.

Signed-off-by: Denton Gentry <dgentry@tailscale.com>

.github/workflows/cifuzz.yml

@@ -1,5 +1,7 @@
 name: CIFuzz
-on: [pull_request]
+on:
+  push:
+    branches: [ main, release-branch/* ]
 
 concurrency:
   group: ${{ github.workflow }}-$${{ github.head_ref || github.run_id }}
@@ -7,7 +9,7 @@ concurrency:
 
 jobs:
   Fuzzing:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
     steps:
     - name: Build Fuzzers
       id: build
@@ -20,7 +22,7 @@ jobs:
       uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
       with:
         oss-fuzz-project-name: 'tailscale'
-        fuzz-seconds: 300
+        fuzz-seconds: 900
         dry-run: false
         language: go
     - name: Upload Crash

.github/workflows/codeql-analysis.yml

@@ -27,7 +27,7 @@ concurrency:
 jobs:
   analyze:
     name: Analyze
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
     permissions:
       actions: read
       contents: read

.github/workflows/cross-darwin.yml

@@ -14,7 +14,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
 

.github/workflows/cross-freebsd.yml

@@ -14,7 +14,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
 

.github/workflows/cross-openbsd.yml

@@ -14,7 +14,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
 

.github/workflows/cross-wasm.yml

@@ -14,7 +14,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
 

.github/workflows/cross-windows.yml

@@ -14,7 +14,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
 

.github/workflows/linux-race.yml

@@ -14,7 +14,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
 

.github/workflows/linux.yml

@@ -14,7 +14,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
 
@@ -38,10 +38,6 @@ jobs:
 
     - name: Get QEMU
       run: |
-        # The qemu in Ubuntu 20.04 (Focal) is too old; we need 5.x something
-        # to run Go binaries. 5.2.0 (Debian bullseye) empirically works, and
-        # use this PPA which brings in a modern qemu.
-        sudo add-apt-repository -y ppa:jacob/virtualisation
         sudo apt-get -y update
         sudo apt-get -y install qemu-user
 

.github/workflows/linux32.yml

@@ -14,7 +14,7 @@ concurrency:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
 

.github/workflows/static-analysis.yml

@@ -40,7 +40,7 @@ jobs:
       if: failure() && github.event_name == 'push'
 
   vet:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
     steps:
     - name: Set up Go
       uses: actions/setup-go@v3
@@ -66,7 +66,7 @@ jobs:
       if: failure() && github.event_name == 'push'
 
   staticcheck:
-    runs-on: ubuntu-latest
+    runs-on: buildjet-4vcpu-ubuntu-2204
     strategy:
       matrix:
         goos: [linux, windows, darwin]

.github/workflows/vm.yml

@@ -11,7 +11,7 @@ concurrency:
 
 jobs:
   ubuntu2004-LTS-cloud-base:
-    runs-on: [ self-hosted, linux, vm ]
+    runs-on: buildjet-4vcpu-ubuntu-2204
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
 
@@ -27,12 +27,17 @@ jobs:
         with:
           go-version-file: go.mod
 
+      - name: Get QEMU
+        run: |
+          sudo apt-get -y update
+          sudo apt-get -y install qemu-system-x86 qemu-user genisoimage qemu-utils
+
       - name: Run VM tests
         run: go test ./tstest/integration/vms -v -no-s3 -run-vm-tests -run=TestRunUbuntu2004
         env:
           HOME: "/tmp"
           TMPDIR: "/tmp"
-          XDG_CACHE_HOME: "/var/lib/ghrunner/cache"
+          XDG_CACHE_HOME: "/home/runner/cache"
 
       - uses: k0kubun/action-slack@v2.0.0
         with:

.github/workflows/windows.yml

@@ -14,7 +14,7 @@ concurrency:
 
 jobs:
   test:
-    runs-on: windows-latest
+    runs-on: [ self-hosted, Windows ]
 
     if: "!contains(github.event.head_commit.message, '[ci skip]')"