[SPIRV] Investigate usage of `report_fatal_error` in `SPIRVInstructionSelector`

[inbelic]

Throughout SPIRVInstructionSelector there are many uses of report_fatal_error to indicate various errors, however, none of these have any associated testing.

As part of #123853, this pattern was propagated to report an error and a test was added to ensure the correct error message was received. This caused the hwasan build bot to fail.

It is assumed that all of the other report_fatal_error instances would cause a similar failure if executed on the build-bot, or at the least, the other instance that outputs a diagnostics message printing out the current instruction here.

This issue is to track an investigation of which uses of report_fatal_error cause the sanitization build-bot to fail, and apply a fix correspondingly.

Of the top of my head some potential things to check are:
We don't seem to return false after reporting a fatal error
We have allocated a diag message to output through a locally constructed output_stream.

AC:

• Reproduce the failing test-case locally: https://github.com/google/sanitizers/wiki/SanitizerBotReproduceBuild
• Write testing for various report_fatal_error messages
• Determine the issue to the bug. Some potential things to check listed above.
• Ideally produce a fix and add test-cases to demonstrate as such.

[Icohedron]

I will investigate this issue