Auto merge of #137081 - Shourya742:2025-02-15-change-config.toml-to-bootstrap.toml, r=onur-ozkan,jieyouxu,kobzol

change config.toml to bootstrap.toml

Currently, both Bootstrap and Cargo uses same name as their configuration file, which can be confusing. This PR is based on a discussion to rename `config.toml` to `bootstrap.toml` for Bootstrap. Closes: https://github.com/rust-lang/rust/issues/126875.

I have split the PR into atomic commits to make it easier to review. Once the changes are finalized, I will squash them. I am particularly concerned about the changes made to modules that are not part of Bootstrap. How should we handle those changes? Should we ping the respective maintainers?