Use the Go module information built into the binary if the Build var
wasn't set during the build.
This means if you install via a specific tag, you get:
go install github.com/slackhq/nebula/cmd/nebula@v1.9.5
$ nebula -version
Version: 1.9.5
And if you install master, you get:
go install github.com/slackhq/nebula/cmd/nebula@master
$ nebula -version
Version: 1.9.5-0.20250408154034-18279ed17b10
These new helpers make the code a lot cleaner. I confirmed that the
simple helpers like `atomic.Int64` don't add any extra overhead as they
get inlined by the compiler. `atomic.Pointer` adds an extra method call
as it no longer gets inlined, but we aren't using these on the hot path
so it is probably okay.
* enforce the use of goimports
Instead of enforcing `gofmt`, enforce `goimports`, which also asserts
a separate section for non-builtin packages.
* run `goimports` everywhere
* exclude generated .pb.go files
