Regression test for #19434 which appear to be fixed.

	Respect user settings around 'Blocks' when adding parameter null checks.

Made OOP to handle initial solution case better and made it to have better perf.

Be resilient to documents/projects with null-filepaths in our persistence layer.

Do not pass around null SymbolTreeIndices.  Instead, pass around empty ones.

Merge Features/async main

tests only. no ask mode approval is required. thanks!

Closes:#19434

Use-throw-expression should not be offered when the 'if-block' has additional statements in it

Pool the simplifiers we use when simplifying code.

Preserve trivia when converting a numeric literal base

* remove remaining prototype comments, add extension method tests

* fix old test, address review feedback

* ReturnType implemented on each subclass

* added more tests on non-async task returning mains

* add obsolete tests

* autoformat

* add better tests for successful task overrides

Fixes #19280