build(deps): upgrade indexmap crate

[Conaclos]

Summary

Upgrade indexmap to 2.x
Only schemars (a dev dependency) requires indexmap 1.x.
Thus, we can upgrade to indexmap 2.x

I also enabled the serde feature of indexmap to remove our custom serde implementations. Unfortunately, we cannot remove STringSet` because schemars don't provide schemas for indexmap 2.x

It seems that we use IndexMap in cases where we could use a HashSet or a sorted Vec.
A future PR should investigate some possible implications / perf improvements.

Test Plan

CI must pass.

[codspeed-hq]

CodSpeed Performance Report

Merging #2673 will not alter performance

_{Comparing conaclos/upgrade-indexmap (f20ebfd) with main (47662b3)}

Summary

✅ 88 untouched benchmarks

[arendjr]

It seems that we use IndexMap in cases where we could use a HashSet or a sorted Vec.

Do you have examples of where that’s the case? Generally I’m hesitant with HashSet/HashMap because I don’t like undefined ordering, which is notorious for creating situations with hard-to-reproduce bugs that only manifest in certain situations based on ordering.

Of course sorted Vecs don’t have that problem and are indeed sufficient in many cases, though I often reach for BTreeMap/BTreeSet too.

[Conaclos]

Do you have examples of where that’s the case? Generally I’m hesitant with HashSet/HashMap because I don’t like undefined ordering, which is notorious for creating situations with hard-to-reproduce bugs that only manifest in certain situations based on ordering.

For example in the path interner or for storing the globals js config.
In these two cases, we could use a (Fx)HashSet.