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.
-- v7: tests: Remove [require] directives for tests that use int and bool uniforms.