Bring existing compiler team repositories up-to-code.

[davidtwco]

This issue originally only aimed to unify the labels across compiler team crates, but was generalized to list all of the things listed in the out-of-tree crates policy. The original description is below.

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In order to perform triage in the weekly meeting across nominated issues in all compiler-team maintained repositories, we should make sure that there are a consistent set of labels that are used and that we update the triage meeting agenda to point to these searches.

[davidtwco]

Having a quick look, I think these are the relevant repositories:

• rust-lang/rust
• rust-lang/rustc-guide
• rust-lang/miri
• rust-lang/compiler-team
• rust-lang/measureme
• rust-lang/chalk
• rust-lang/polonius
• rust-lang/rustc-rayon
• rust-lang/rustc-hash
• rust-lang/wg-traits
• rust-lang/datafrog
• rust-lang/llvm (archived)
• rust-lang/lldb (archived)
• rust-lang/rust-forge (maybe?)
• rust-lang/llvm-project (maybe?)
• rust-lang/rls (maybe?)
• rust-lang/gll (maybe?)

And these are the relevant labels that would need to be on each repo: P-high, P-med, P-low, T-compiler and I-nominated. Not sure about these, might just be relevant for rust-lang/rust: regression-from-stable-to-beta, regression-from-stable-to-beta, beta-nominated and stable-nominated.

[davidtwco]

We want to make sure that all compiler team maintained repositories match the out-of-tree crates policy, that means making sure that the repositories on this list have the following:

• GitHub permissions (Compiler team with write, Assignees with read)
• README describing intended purpose of the crate, who maintains it and intended level of stability and maintenance.
• LICENSE-MIT and LICENSE-APACHE
• CODE_OF_CONDUCT
• Labels for triage: P-high, P-med, P-low, T-compiler and I-nominated.
• @rust-highfive