Make StackTraceHelper tests runtime-agnostic

[medhatiwari]

Summary

Fixes the remaining 2 failing StackTraceHelper tests from #63927 by making tests runtime-agnostic instead of expecting exact string matches for runtime internals.

Problem

Tests were failing on Mono due to strict string matching against runtime-specific formatting:

• Lambda methods: Expected "lambda_method34" but Mono shows "object.lambda_method34"
• Async state machines: Expected resolved method names but Mono shows state machine internals

Solution

Updated tests to verify essential functionality while accepting different valid runtime behaviors:

• Lambda test: Changed from Assert.StartsWith("lambda_method") to Assert.Contains("lambda_method")
• Async test: Added flexible checks that accept both resolved method names and state machine forms

cc: @giritrivedi

[joperezr]

While you are still verifying that key components are present, it does mean that we are a bit less strict in CoreCLR which could be a potential for regressions. Would it make sense to instead of relaxing some of these matches, to instead first do a Runtime check to see if running under CoreCLR or Mono, and then if CoreCLR we keep the stricter checks but for Mono we just validate key components? This way you are not losing any regression coverage, but you are making the tests pass on more runtimes.

[medhatiwari]

@joperezr Good point! I've updated it with runtime-specific assertions as you suggested

[joperezr]

Thank you so much for your contribution @medhatiwari! Left a small comment that would be good if you could address, but otherwise this is looking really good 😃

[medhatiwari]

Thank you so much for your contribution @medhatiwari! Left a small comment that would be good if you could address, but otherwise this is looking really good 😃

Thanks for reviewing the PR