Combine re_types integration tests into one test target.

[kpreid]

What

This significantly reduces (re)build times and total artifact size for these tests as a whole; the combined target is only ~4 times bigger (in time and space) than each of the 19 single-archetype test targets it replaces.

A disadvantage is that now tests/types/main.rs needs to list child modules. If desired, this could be added to the code generator; the cfgs in main.rs could equally well be moved inside each module to make the file completely regular.

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!
• If have noted any breaking changes to the log API in CHANGELOG.md and the migration guide

• PR Build Summary
• Recent benchmark results
• Wasm size tracking

To run all checks from main, comment on the PR with @rerun-bot full-check.

[emilk]

Nice!