[PATCH 0/5] MR616: tests: Improvements for SM1 testing.

[Francisco Casas (＠fcasas)]

This is the first part of !608, which I decided to separate to ease review.

It consists of improvements to SM1 testing, mainly:
- Correctly passing int and bool uniforms as IEEE 754 floats to SM1 profiles.
- The introduction of the "only" qualifier to avoid abusing `[require]` blocks in case tests retrieve different results for different shader models.
- Allowing some of the tests we already have for SM4/SM6 to run in SM1 after those improvements.