feat: Only flycheck workspace that belongs to saved file
Supercedes https://github.com/rust-lang/rust-analyzer/pull/11038
There is still the problem that all the diagnostics are cleared, only clearing diagnostics of the relevant workspace isn't easily doable though I think, will have to dig into that
Cargo will always output something on success:
```
$ cargo check --message-format=json
{"reason":"compiler-artifact", ... snipped ... }
{"reason":"build-finished","success":true}
```
However, rustc does not output anything on success:
```
$ rustc --error-format=json main.rs
$ echo $?
0
```
Restore the behaviour prior to #10517, where an exit code of 0 is
considered good even if nothing is written to stdout.
This enables custom overrideCommand values that use rustc rather than
cargo.
The thread name is shown in debugger as well as panic messages and this
patch makes it easier to follow a thread instead of looking through
full backtrace, by naming all spawned threads according to their
functioning.
Cargo commands are affected by the `.cargo/config` files above
their working directory. If cargo is invoked from above the directory
holding `Cargo.toml`, it may not pick up important settings like
registry replacements, causing it to behave differently or even fail.
Most cargo invocations are currently setting their working directories
to the directory containing `Cargo.toml`, but a couple of paths remain
in which cargo is invoked from the default workspace root instead.
This change fixes that, resolving some cargo check failures that I
experienced in a multi-root workspace in which packages used different
registries.
