We're no longer compiling the entire CLI for WASM, so we can remove
some wrapper functions and GOOS checks.
Effectively reverts 75de4e9cc2020f9d5bc60de3b78937dd405b03f5.
5df7ac70d6a942d1bd4cb5b388aecbe161a1a0d1, eda647cb47dc0f8dea58cb6127944fdd071990fd
and other changes.
Fixes#5146
Signed-off-by: Mihai Parparita <mihai@tailscale.com>