Simplify and reuse code around temp dirs in FSharp.Compiler.Service.Tests

[majocha]

Description

TestFramework module from Test.Utilities provides functionality for creating and cleanup of temp directories and files for testing.
There is a lot of similar code in FSharp.Compiler.Service.Tests that can be simplified now.

Fixes

Some flakiness around creating deleting / directories, for example:
https://dev.azure.com/dnceng-public/public/_build/results?buildId=875794&view=logs&j=170942dc-5349-5022-2275-77744f335216&t=20776a93-33c2-52f0-ee8f-b8c9809b2e23&l=16230

  Failed FSharp.Compiler.Service.Tests.ExprTests.Test Operator Declarations for IntPtr [5 ms]
  Error Message:
   System.IO.DirectoryNotFoundException : Could not find a part of the path 'C:\Users\cloudtest\AppData\Local\Temp\FSharp.Test.Utilities\ab3ae841\ExprTests\92147ee0_8116_18.fs'.

[github-actions]

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