[WIP] Reuse typechecking results - stage 1

[psfinaki]

First part of the implementation of reusing typecheck results, as per the design doc.

This basically does 2 things:

• adds the flag --reusetypecheckingresults, with all the hooking
• force-generates the typechecking graph and skips recompilation if it's unchanged

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Open questions: see my comments.

[github-actions[bot]]

:heavy_exclamation_mark: Release notes required

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:white_check_mark: Found changes and release notes in following paths:

[!WARNING] No PR link found in some release notes, please consider adding it.

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/9.0.200.md	No current pull request URL (https://github.com/dotnet/fsharp/pull/17898) found, please consider adding it

[psfinaki]

@T-Gro PTAL, this is an early stage so I mostly just wanted to discuss the questions I raised in the comments, so that we go in the agreed direction.

[edgarfgp]

It seems like this is going to rely/build on top of graph checking have couple questions:

• Would this PR https://github.com/dotnet/fsharp/pull/17442 be included ?
• If we are going to rely on this would be important to enable by default ?

[psfinaki]

@edgarfgp so we'll need to discuss this - personally I'd like to turn graph-checking on. Now (like, before Xmas) is a rather good time - we can catch some bugs there before the next big release.

It's somewhat scaring but, well, just this probably shouldn't be stopping us 👀 Graph-checking and reusing typechecking results can test each other and I'd say we should use this benefit here.

I am not speaking for the whole team just yet - only sharing some thoughts. We will discuss and prioritize this.

[psfinaki]

Merging, since this goes to a feature branch now.