Add progress indication for `Updating crates.io index`

[RunDevelopment]

Hello! I recently opened a Rust workspace, and Rust Analyzer just did something for 10 minutes. There was no progress indication, just a "Fetching" (or was it "Fetching index") with a spinner. No 1/X, no x% done, no logs (in VSCode > Tasks > RA).

Since I had no idea what it was doing (what does "Fetching index" mean?), I opened Task manager and killed its cargo progress. For all that I knew, cargo could have been stuck in an infinite loop of some kind. After I did that, RA complained, logging that some cargo command failed to execute, and restarted cargo. And there I was back to waiting, with no progress indication, still having no idea what it was doing.

So what happened? Cargo was Updating crates.io index. It was resolving/downloading 90k deltas since I hadn't used that version of Rust for a while (I have multiple rust tool chains installed), and that took some time. Around 20 minutes. Even on my more commonly-used tool chains, updating the index regularly takes multiple seconds and up to a minute on my machine (I have slow internet).

Please add progress indication for updating the crates.io index.

[Veykril]

That's probably hitting this

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

Lines 283 to 286 in 983094a

	// FIXME: Fetching metadata is a slow process, as it might require
	// calling crates.io. We should be reporting progress here, but it's
	// unclear whether cargo itself supports it.
	progress("metadata".to_string());

So this is blocked on cargo metadata somehow allowing us to do that.

[lnicola]

Note that newer Cargo will use a faster access method. What toolchain are you using?

[RunDevelopment]

In the especially slow case, I was using 1.67.0, so that's likely before the sparse index. On the other toolchain, I'm using 1.71.0.

[Jaxx4Fun]

+1.
Especially for those who are connected to blocked/slow network, it's too unclear for us to identify the root cause. Whether it's because the network issue, or the crates to be updated are too many that makes it cost so long.

BTW I'm using cargo 1.74.0 but it still shows only "fetch metadata" for almost 10 minutes.