Rollup merge of #136581 - jieyouxu:makefile-be-gone, r=Kobzol

Retire the legacy `Makefile`-based `run-make` test infra

The final piece of [porting run-make tests to use Rust #121876](rust-lang/rust#121876).
Closes #121876.
Closes #40713.
Closes #81791 (no longer using `wc`).
Closes #56475 (no longer a problem in current form of that test; we don't ignore the test on `aarch64-unknown-linux-gnu`).

### Summary

This PR removes the legacy `Makefile`-based `run-make` test infra which has served us well over the years. The legacy infra is no longer needed since we ported all of `Makefile`-based `run-make` tests to the new `rmake.rs` infra.

Additionally, this PR:

- Removes `tests/run-make/tools.mk` since no more `Makefile`-based tests remain.
- Updates `tests/run-make/README.md` and rustc-dev-guide docs to remove mention about `Makefile`-based `run-make` tests
- Update test suite requirements in rustc-dev-guide on Windows to no longer need MSYS2 (they should also now run successfully on native Windows MSVC).
- Update `triagebot.toml` to stop backlinking to #121876.

**Thanks to everyone who helped in this effort to modernize the `run-make` test infra and test suite!**

r? bootstrap

Author: jieyouxu