refactor: replace InternedString with Cow in IndexPackage

[0xPoe]

What does this PR try to resolve?

ref #14834

As described in the issue, we want to move IndexPackage into cargo-util-schemas. However, it contains InternedString fields, which we don't want to expose as part of the public API.
This PR replaces InternedString with Cow.

How should we test and review this PR?

It shouldn't change or break any tests.

Additional information

None

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[ehuss]

I would recommend at least doing some benchmarking using our bench suite. https://github.com/rust-lang/cargo/tree/master/benches contains some documentation, and particularly the resolve bench. cargo bench -p benchsuite --bench resolve is a good place to start (while you are figuring out how to run the benchmarks you can do an individual workspace like resolve_ws/rust to speed things up), and Comparing implementation explains how you can do a comparison report against master.

[0xPoe]

WIP: I need to do more tests

I’ve tested this change several times using the resolve_ws/rust benchmark suite.

My test env:

  Model Name:	MacBook Pro
  Chip:	Apple M4 Max
  Total Number of Cores:	14 (10 performance and 4 efficiency)
  Memory:	36 GB

Test result:
master commit: HEAD is now at c2c636a fix(toml): Remove workaround for rustc frontmatter support (#15570)
master: cargo bench -p benchsuite --bench resolve -- resolve_ws/rust --save-baseline master --measurement-time 50 --sample-size 500
patch: cargo bench -p benchsuite --bench resolve -- resolve_ws/rust --baseline master --measurement-time 50 --sample-size 500

First round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/rust	98.328 ms	+0.9865%	20 (4.00%) - 16 high mild, 4 high severe
resolve_ws/rust-ws-inherit	97.151 ms	-0.5031%	25 (5.00%) - 19 high mild, 6 high severe

Second round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/rust	97.223 ms	+0.7313%	11 (2.20%) - 9 high mild, 2 high severe
resolve_ws/rust-ws-inherit	96.244 ms	+0.1513%	11 (2.20%) - 10 high mild, 1 high severe

Third round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/rust	96.765 ms	+1.2520%	14 (2.80%) - 11 high mild, 3 high severe
resolve_ws/rust-ws-inherit	96.107 ms	+0.7632%	13 (2.60%) - 12 high mild, 1 high severe

Fourth round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/rust	96.226 ms	-0.8911%	9 (1.80%) - 7 high mild, 2 high severe
resolve_ws/rust-ws-inherit	95.999 ms	-0.7607%	18 (3.60%) - 14 high mild, 4 high severe

[weihanglo]

I wonder if we could change InternString::from_cow to something like:

impl<'a> From<Cow<'a, str>> for InternedString {
    fn from(cs: Cow<'a, str>) -> Self {
        let mut cache = interned_storage();
        let s = cache.get(cs.as_ref()).copied().unwrap_or_else(|| {
            let s = cs.into_owned().leak();
            cache.insert(s);
            s
        });

        InternedString { inner: s }
    }
}

So in other places we can rely on Into<InternedString>.