Switched to subtests using `t.Run()` for GUID testing, rather than using
log statements to demarcate different tests.
Added `.String` to GUID `Variant` and `Version` using
`golang.org/x/tools/cmd/stringer`.
Added `tools.go` to version `stringer` in go.mod and allow
`go generate ./...` to be run without needing a `go get` call.
Based off of [go wiki](https://github.com/golang/go/wiki/Modules#how-can-i-track-tool-dependencies-for-a-module)
recommendation.
Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>
Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>
