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.
Without this users have no clue why flycheck fails to run.
This is what is printed to the output channel:
```
[ERROR rust_analyzer::main_loop] cargo check failed: Cargo watcher failed,the command produced no valid metadata (exit code: ExitStatus(ExitStatus(25856)))
```
I stumbled with this figuring out that rust-analyzer adds `--all-features` which is not intended
for some crates in the workspace (e.g. they have mutually-exclusive features.
Having the command rust-analyzer ran should help a lot
