Support #exit;; as alias to #quit;; in fsi

[bbatsov]

Users often type #exit;; out of habit from shells and .NET's exit(). This adds #exit as an alias alongside #q and #quit, and includes it in the #help output.

Fixes #18820

[github-actions]

❗ Release notes required

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✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/10.0.300.md

[bbatsov]

I have to say I was amused to see that the comment for quit was // Exit. :-) Anyways, I'm reasonably sure I got this one right, but as always I'm looking forward to your feedback!

[T-Gro]

I appreciate this addition - I frequently had to stop and remember how quit is spelled, exit is way easier 👍 .
There is DependencyManagerInteractiveTests also verifying help output - you can also decide to change that test's assertion to stop firing in any fsi help extension (since the test is about dependency manager).

[bbatsov]

Will do!