`#[rust_analyzer::*]` tool and lint attributes

NOTE: Implementation of some of these has started but we do not make any stability guarantees about these attributes for now, so they may change over time.

• https://github.com/rust-lang/rust/issues/66079

This serves as a general bag of ideas around possible future r-a/ide tool attributes (we have this attribute now https://github.com/rust-lang/rust/pull/125241)

• #[rust_analyzer::skip]: cc https://github.com/rust-analyzer/rust-analyzer/issues/7449
• #[rust_analyzer::macro::expands_to(kind0, kind1, ...)] where kind can be anything a macro is allowed to expand to like item, expr, pat, ... This annotation's sole purpose would be to aid completions by allowing us to filter out macros that aren't applicable.
• #[rust_analyzer::crate_prelude] marks a crate's prelude, aids fly-import completions and auto-import features by allowing (via a config) to avoid or prefer crate preludes for imports.
• #[rust_analyzer::rust_fixture_params(param_name1, ...)]: specify parameters of a function that are to be highlighting injected, alternatively mark the parameters with attributes directly, but that might become rather unwieldy -> https://github.com/rust-lang/rust-analyzer/pull/18906
• #[rust_analyzer::macro::expansion_type(path::to::type)]: https://github.com/rust-analyzer/rust-analyzer/issues/10913
• #[rust_analyzer::unsafe_macro]: https://www.reddit.com/r/rust/comments/vftkrm/unsafe_code_highlighting_with_rustanalyzer/icy0jlv/
• #[rust_analyzer::render_as_impl_trait]: annotation for types to render them as impl Trait, like we do by default for std types that implement Iterator
• #[rust_analyzer::color(args)]: https://github.com/rust-lang/rust-analyzer/issues/13122
• #[rust_analyzer::resolve_hint(path::to::something): Will make r-a attempt to resolve the given path, useful for macros to output to so that tokens they full consume can be remapped to a resolving path.
• #[rust_analyzer::runnable(command arg arg ....)): Will make r-a recognize this as a runnable action (like fn main() or #[test] fn test), putting a runnable lens on top that executes the command with the given args
• #[rust_analyzer::macro_expansion_token_limit(10000)]: Sets the expansion token limit for the crate or annotated macro call
• #[rust_analyzer::enum_happy_variant]: Annotate variants to handle them like Some or Ok for assist purposes, https://github.com/rust-lang/rust-analyzer/blob/d6d735e6f20ef78b16a79886fe28bd69cf059504/crates/ide-db/src/ty_filter.rs

Note: names are of course bikesheddable

Begin by reviewing the existing attribute from rust-lang/rust#125241 and the linked rust-analyzer issues, then inspect crates/ide-db/src/ty_filter.rs for the enum-variant assist behavior. This issue is a broad list of proposals, so completion would require selecting one attribute, defining its scope and behavior, and adding the relevant implementation and tests.