all: use zstdframe where sensible (#11491)

Use the zstdframe package where sensible instead of plumbing
around our own zstd.Encoder just for stateless operations.

This causes logtail to have a dependency on zstd,
but that's arguably okay since zstd support is implicit
to the protocol between a client and the logging service.
Also, virtually every caller to logger.NewLogger was
manually setting up a zstd.Encoder anyways,
meaning that zstd was functionally always a dependency.

Updates #cleanup
Updates tailscale/corp#18514

Signed-off-by: Joe Tsai <joetsai@digital-static.net>

wgengine/netlog/logger.go

@@ -22,7 +22,6 @@ import (
 	"tailscale.com/net/netmon"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tsaddr"
-	"tailscale.com/smallzstd"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/logid"
 	"tailscale.com/types/netlogtype"
@@ -111,15 +110,9 @@ func (nl *Logger) Startup(nodeID tailcfg.StableNodeID, nodeLogID, domainLogID lo
 		PrivateID:     nodeLogID,
 		CopyPrivateID: domainLogID,
 		Stderr:        io.Discard,
+		CompressLogs:  true,
+		HTTPC:         httpc,
 		// TODO(joetsai): Set Buffer? Use an in-memory buffer for now.
-		NewZstdEncoder: func() logtail.Encoder {
-			w, err := smallzstd.NewEncoder(nil)
-			if err != nil {
-				panic(err)
-			}
-			return w
-		},
-		HTTPC: httpc,
 
 		// Include process sequence numbers to identify missing samples.
 		IncludeProcID:       true,