dev: `gen bazel` after adding a new logictest config may require multiple calls to generate all output

[rickystewart]

Consider this commit. If you run dev gen bazel, one of the steps will add new BUILD.bazel files for the new config, but will not git add them. This means that the later git diff to determine which other steps of the code generation need to run will not find these files and the generate-bazel-extra step, which is necessary to populate pkg/BUILD.bazel with the new tests, will be skipped.

This string of commits plots this behavior, one dev gen after the other. The last dev gen will only update the last file if you git add or commit the files from the earlier run.

One option we have is to in addition to git diff, run git status to enumerate untracked files.

Epic: CRDB-17171

Jira issue: CRDB-44459

[blathers-crl[bot]]

Hi @rickystewart, please add branch-* labels to identify which branch(es) this C-bug affects.

_{:owl: Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}