TUN-5551: Reintroduce FIPS compliance for linux amd64 now as separate binaries

This is a cherry-pick of 157f5d1412
followed by build/CI changes so that amd64/linux FIPS compliance is
provided by new/separate binaries/artifacts/packages.

The reasoning being that FIPS compliance places excessive requirements
in the encryption algorithms used for regular users that do not care
about that. This can cause cloudflared to reject HTTPS origins that
would otherwise be accepted without FIPS checks.

This way, by having separate binaries, existing ones remain as they
were, and only FIPS-needy users will opt-in to the new FIPS binaries.

token/launch_browser_darwin.go

@@ -1,4 +1,5 @@
-//+build darwin
+//go:build darwin
+// +build darwin
 
 package token
 

token/launch_browser_other.go

@@ -1,4 +1,5 @@
-//+build !windows,!darwin,!linux,!netbsd,!freebsd,!openbsd
+//go:build !windows && !darwin && !linux && !netbsd && !freebsd && !openbsd
+// +build !windows,!darwin,!linux,!netbsd,!freebsd,!openbsd
 
 package token
 

token/launch_browser_unix.go

@@ -1,4 +1,5 @@
-//+build linux freebsd openbsd netbsd
+//go:build linux || freebsd || openbsd || netbsd
+// +build linux freebsd openbsd netbsd
 
 package token
 

token/launch_browser_windows.go

@@ -1,4 +1,5 @@
-//+build windows
+//go:build windows
+// +build windows
 
 package token
 

token/token_test.go

@@ -1,3 +1,4 @@
+//go:build linux
 // +build linux
 
 package token