Some minor perf improvements

[nojaf]

Description

Some things that got detected by the work happening in ionide/ionide-analyzers#85

Checklist

• Test cases added

• Performance benchmarks added in case of performance changes

• Release notes entry updated:

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  • Correctly handle assembly imports with public key token of 0 length. (Issue #16359, PR #16363)
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[github-actions]

❗ Release notes required

@nojaf,

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Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/8.0.300.md	No release notes found or release notes format is not correct

[majocha]

isNotNull ?

fsharp/src/Compiler/Utilities/illib.fs

Line 88 in 890e6e1

let inline isNotNull (x: 'T) = not (isNull x)

[vzarytovskii]

These are covered in @psfinaki PR likely, and we decided to wait with changes for a bit, since we already have some SO reports in compiler and those need careful verification.

[vzarytovskii]

#16822

[vzarytovskii]

Reason to postpone it is here: #16316 (comment)
There were stackoverflows when allocating more things on stack in certain cases. We will need to make sure we aren't hitting (or won't be hitting) it with AP changes.