Add convience functions for creating TlasInstances

[Vecvec]

Connections

None

Description

I almost never use the more complex parts of tlas instances, and frequently don't use transforms. This makes it painful to write tlas instance building in simple cases, and also annoying to read and debug the code (I've used NSight and PIX more often to debug why my instances aren't showing up [and then finding that is was because I had mis-typed my matrix so that they were a point or I had swapped the mask and custom data] than any other problem). I think it makes sense to add functions for two common simple uses - a full mask and no custom data + a blas + transform and a full mask and no custom data with identity transform + a blas. This can also help prevent breaking changes as things like new flags and instance intersection group indices can be left out of these new functions.

The names are a bit more annoying. Hopefully this can all be reworked w/ default field values, but that still seems to be some time away.

Testing

Changed most tests to use these where possible.

Squash or Rebase?

Squash

LLM Use?

None

Checklist

• I self-reviewed and fully understand this PR.
• CHANGELOG.md entries for the user-facing effects of this change are present.
• The PR is minimal, and doesn't make sense to land as multiple PRs.
• Commits are logically scoped and individually reviewable.
• The PR description has enough context to understand the motivation and solution implemented.