chore: make repo bazel aware & add microgen macro

[noahdietz]

Fixes #148

• BUILD files generated by gazelle
• Go deps in WORKSPACE generated based on go.mod
• rules_go_gapic/go_gapic.bzl introduces the first pass at a macro that runs the microgenerator in this repo

[noahdietz]

I'd like guidance on the macro & workspace naming. I kind of copied the monolith's macros/rules

[vam-google]

In general looks good.
One thing which I did not realize was how much bazel boilerplate code gazelle will generate... It is probably better to keep it like this (since there is special tool to generate it), but it is worth mentioning that it could be a single hand-written BUILD.bazel file for the whole repo (gazelle just tries to be very strict about best practices, generating BUILD.bazel for each package, which makes the boilerplate code "explode"). A hand-written bazel build file will make the build look much less scary =)

[vam-google]

just curious why there are 2 urls for each? Is this how they recomend it now in rules_go docs?

[noahdietz]

I copied this from the gazelle repo: https://github.com/bazelbuild/bazel-gazelle#running-gazelle-with-bazel

I can fiddle with removing one if you think its an anti-pattern? LMK

[vam-google]

LGTM with a comment.
Also, please make sure that it works with bazel-1.0.0 (released recently).

[vam-google]

LGTM (with the tiny string concatenation change we discussed offline)