Improve static compilation of state machines

[majocha]

Fixes #19296, also includes test cases from #14930, brazenly vibecoded.

However I think the risk of changes here is under control, given that we have quite a few relevant projects and their tests in the regression matrix.

OK here goes AI summary:

This pull request improves the F# compiler's handling of state machine lowering, especially for cases involving resumable code and control flow constructs like if __useResumableCode. It fixes issues where inlined helpers or nested resumable code constructs could incorrectly fall back to dynamic branches at runtime, and adds comprehensive test coverage for these scenarios. The main focus is on ensuring that statically-compilable state machines are correctly recognized and optimized, and that code generation remains robust for complex patterns.

Key changes include:

Compiler logic improvements:

• Enhanced the lowering pass in LowerStateMachines.fs to correctly handle resumable code bindings found inside debug points, ensuring that nested resumable code constructs are properly expanded.
• Updated the reduction logic to track locally-bound resumable code continuations in the environment, allowing correct resolution and inlining of these continuations during optimization. [1] [2]
• Modified the rewrite environment to avoid recursing into nested state machine expressions, preventing unintended modification of their internal logic and ensuring that only the appropriate static branches are taken for if __useResumableCode.

Test suite enhancements:

• Added a new test module (FailingInlinedHelper) and test case to verify that inlined helpers containing if __useResumableCode are expanded correctly, addressing a real-world bug. [1] [2]
• Expanded tests to cover additional scenarios involving for-loops over tuples and various statically-compilable task patterns, ensuring robust handling of these constructs.

Documentation/test comments:

• Updated comments in the NestedTaskFailures.fs test to reflect that certain state machine failures are now fixed, clarifying the status of known issues.Fixes State machines: low-level resumable code not always expanded correctly, without warning #19296, also includes test cases from Try fix static compilation of state machines #14930

[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

[majocha]

Looks like this now to some point reinvents #14930. I'll try to include some of the relevant repros in tests. Too bad they are scattered across issues and comments.

[majocha]

Another observation: Lack of FS3511 warning does not mean the state machine actually compiled statically. Sometimes the fallback to dynamic implementation gives no warning.

[majocha]

This issue is fixed now.

[majocha]

State machines sometimes fallback to dynamic implmentation without FS3511 warning. Checking for generated MoveNext is more reliable.