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

[rustbot]

r? @ehuss

rustbot has assigned @ehuss.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[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]

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	91.910 ms	-0.9313%	31 (6.20%) - 14 high mild, 16 high severe
resolve_ws/rust-ws-inherit	92.021 ms	+0.7503%	43 (8.60%) - 14 high mild, 22 high severe

Second round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/rust	92.142 ms	+1.7303%	33 (6.60%) - 10 high mild, 23 high severe
resolve_ws/rust-ws-inherit	91.193 ms	-0.0707%	30 (6.00%) - 8 high mild, 22 high severe

Third round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/rust	91.398 ms	+1.2693%	28 (5.60%) - 8 high mild, 20 high severe
resolve_ws/rust-ws-inherit	90.558 ms	+0.5349%	26 (5.20%) - 8 high mild, 18 high severe

Fourth round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/rust	91.193 ms	+0.8302%	26 (5.20%) - 11 high mild, 15 high severe
resolve_ws/rust-ws-inherit	90.591 ms	+0.8267%	34 (6.80%) - 6 high mild, 17 high severe

[0xPoe]

I’ve tested this change several times using the resolve_ws/tikv 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/tikv --save-baseline master --measurement-time 100 --sample-size 600
patch: cargo bench -p benchsuite --bench resolve -- resolve_ws/tikv --baseline master --measurement-time 100 --sample-size 600

First round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/tikv	131.32 ms	-2.4203%	42 (7.00%) - 18 high mild, 24 high severe

Second round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/tikv	133.14 ms	+0.8323%	37 (6.17%) - 14 high mild, 23 high severe

Third round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/tikv	134.06 ms	+0.9986%	30 (5.00%) - 10 high mild, 20 high severe

Fourth round:

Benchmark	Time (mean)	Change	Outliers
resolve_ws/tikv	135.27 ms	+2.3135%	106 (17.67%) - 71 high mild, 35 high severe