f88bfa34e1
Remove valgrind test suite and support from compiletest, bootstrap and opt-dist
The `run-pass-valgrind` test suite is not exercised in CI, and as far as I'm aware nobody runs it (asked in https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Are.20the.20valgrind.20tests.20even.20used.20by.20anyone.3F). What's remaining of valgrind support in compiletest isn't even properly hooked up with bootstrap.
The existing valgrind logic in compiletest is also straight up questionable, i.e.
1b3b8e7b02/src/tools/compiletest/src/runtest/valgrind.rs (L7-L12)
It just runs valgrind tests as `rpass` if no valgrind path is provided to compiletest from bootstrap -- but bootstrap doesn't even pass a valgrind path to compiletest in the first place, so this always ran as `rpass` tests. So what is this even testing?
So if it's not testing anything, let's delete it.
Closes #44816 by deleting the test suite :3
<img src="https://github.com/user-attachments/assets/99525bf7-e85b-40ba-9281-e4e1e275c4e8" width=300 />