rust-analyzer doesn't read [env] values from .cargo/config.toml

[recatek]

I'm using environment variables to configure proc macros that need to open and parse files for generation. When building in cargo, I can set these in the [env] block of .cargo/config.toml. However, rust-analyzer doesn't read these environment variables, forcing me to duplicate them as settings with rust-analyzer.server.extraEnv.

rust-analyzer version: rust-analyzer version: 0.3.1369-standalone
rustc version: rustc 1.66.0 (69f9c33d7 2022-12-12)

[Veykril]

Two things here, we should fetch the env section via cargo config get like we do here

rust-analyzer/crates/project-model/src/cargo_workspace.rs

Lines 522 to 525 in 03f676e

	cargo_config
	.current_dir(cargo_toml.parent())
	.args(["-Z", "unstable-options", "config", "get", "build.target"])
	.env("RUSTC_BOOTSTRAP", "1");

and then pass these to where we start the proc-macro server. (We should also make sure that env! expansion checks these vars).

The other thing is that we should watch the .cargo/config.toml for changes and re-fetch the section(s) on change.