internal: add `library` fixture meta
Currently, there is no way to specify `CrateOrigin` of a file fixture ([this] might be a bug?). This PR adds `library` meta to explicitly specify the fixture to be `CrateOrigin::Library` and also makes sure crates that belong to a library source root are set `CrateOrigin::Library`.
(`library` isn't really the best name. It essentially means that the crate is outside workspace but `non_workspace_member` feels a bit too long. Suggestions for the better name would be appreciated)
Additionally:
- documents the fixture meta syntax as thoroughly as possible
- refactors relevant code
[this]: 4b06d3c595/crates/base-db/src/fixture.rs (L450)
internal: support `#[rustc_coinductive]`
rust-lang/rust#100386 changed the trait solver so that `Sized` is treated as coinductive trait, just like auto traits. This is now controlled by the perma-unstable `#[rustc_coinductive]` attribute (rust-lang/rust#108033), which this PR adds support for.
In practice, I don't think this matters much if at all. Currently we don't give chalk enough information so chalk cannot precisely (dis)prove `Sized` bounds.
MIR episode 5
This PR inits drop support (it is very broken at this stage, some things are dropped multiple time, drop scopes are wrong, ...) and adds stdout support (`println!` doesn't work since its expansion is dummy, but `stdout().write(b"hello world\n")` works if you use `RA_SYSROOT_HACK`) for interpreting. There is no useful unit test that it can interpret yet, but it is a good sign that it didn't hit a major road block yet.
In MIR lowering, it adds support for slice pattern and anonymous const blocks, and some fixes so that we can evaluate `SmolStr::new_inline` in const eval. With these changes, 57 failed mir body remains.
MIR episode 2
This PR adds:
1. `need-mut` and `unused-mut` diagnostics
2. `View mir` command which shows MIR for the body under cursor, useful for debugging
3. MIR lowering for or-patterns and for-loops
fix a bunch of clippy lints
fixes a bunch of clippy lints for fun and profit
i'm aware of this repo's position on clippy. The changes are split into separate commits so they can be reviewed separately
