Use yarn instead of npm for JS/TS dependencies

[yotamofek]

Building on @lolbinarycat 's excellent work ( #148672 ).

npm apparently has certain edge-cases where it doesn't actually respect the lockfile it's fed, which has led to at least one CI breakage.

yarn seems to not suffer from those same issues, and also has a --frozen flag for its install command

[rustbot]

This PR modifies src/bootstrap/src/core/config.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

This PR modifies bootstrap.example.toml.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

Some changes occurred in HTML/CSS/JS.

cc @GuillaumeGomez, @jsha, @lolbinarycat

[rustbot]

r? @clubby789

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[yotamofek]

r? @Kobzol since you're already kinda familiar with the situation?

(maybe also @notriddle for the small TS fixes, if you can take a look)

[rustbot]

tidy extra checks were modified.

cc @lolbinarycat

[bors]

☔ The latest upstream changes (presumably #148885) made this pull request unmergeable. Please resolve the merge conflicts.

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[Kobzol]

Since we install yarn using npm anyway (so you need to have node + npm to use yarn), and I assume that it will be more common for people to have npm available locally than having yarn, can we just keep the original npm config and use npm in tidy to install yarn, and then use yarn to install the packages?

[yotamofek]

Apparently, nowadays npm is not the recommended way to install yarn either.

Personally, I think it's fine to expect the few folks actually running tidy's JS (extra)checks to install yarn, if that means we can avoid adding more complexity to tidy.

Regardless of what we choose, I should probably try to modify this PR to install yarn via the new recommended way.

[lolbinarycat]

If we want to automatically install yarn, I think we should do a bit of design work.

Ideally, for everything that we download/install automatically, there would also be a bootstrap config option to specify it's path manually, so that everything can be done offline in something like a nix derivation.

Currently it's not a huge deal bc the only thing we're downloading for without a config option is testing, not building, but it would still be nice.