Improve allocations in evaluations by using ImmutableArray here and there

[rokonec]

Related to #8673

Context

When analyzing traces from VS Orchard evaluation I have noticed few places which are easy to optimize by using ImmutableArray instead of ImmutableList.
ImmutableArray is almost always better in patters loop {mutate by builder}; ToImmutable since it is struct, allocates less, and have faster enumerator.

Changes Made

There are many places where using ImmutableArray instead of ImmutableList would render better performance. I however limit changes only on places which sticks out from memory traces as non-negligable.

Testing

Local. PR gate.

Notes

Overall gain will be small, in percent's of overall allocations, but given relatively simple and safe changes, I think it is good tradeoff.

[ladipro]

Looks good! Would it maybe help if the code used an interface (IEnumerable<T>?) instead of the concrete type to indicate what operations on the collection are actually used?

[ladipro]

Oh, that would mean boxing. Never mind 😀

[rainersigwald]

Yeah, I remember a bunch of "concretize these types to avoid boxing" PRs a few years ago and was about to jump in :)

[rainersigwald]

LGTM but I'd prefer to see the first two commits go in with #8747 and then rebase/squash this.

Also I think ImmutableArray is a good choice here, but we also have access to some Roslyn collections like ImmutableSegmentedList that can be helpful in other cases (here I don't think we're likely to hit the LOH for metadata so the segmentation doesn't help).