SDKv2 Only return a detailed diff if a diff is detected

[VenelinMartinov]

Only return a detailed diff if a diff is detected. This should prevent any mismatches between the detailed diff and the diff decision. Mismatches could only happen in case of a bug somewhere and that might cause issues with the engine.

[VenelinMartinov]

This change is part of the following stack:

• Disable accurate previews for remainder of pf detailed diff tests #2756
  • SDKv2 Only return a detailed diff if a diff is detected #2750 ◀

_{Change managed by git-spice.}

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 68.85%. Comparing base (8313f97) to head (d31fb69).

Files with missing lines	Patch %	Lines
pkg/tfbridge/provider.go	50.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@                          Coverage Diff                           @@
##           vvm/detailed_diff_replace_fallback    #2750      +/-   ##
======================================================================
- Coverage                               68.86%   68.85%   -0.02%     
======================================================================
  Files                                     301      301              
  Lines                                   38765    38765              
======================================================================
- Hits                                    26696    26690       -6     
- Misses                                  10557    10561       +4     
- Partials                                 1512     1514       +2     

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[t0yv0]

Probably reasonable, but wondering if this behavior is under-tested since there's no changes to tests? Can we add a quick one?

[t0yv0]

I'm going to assume the rest of the PR stack provides tests for this but please double check 🙏

[VenelinMartinov]

This would only trigger in the case when the Diff decision and the Detailed Diff do not agree. AFAIK this should only happen in the presence of a bug. I can test this manually by overriding something in the code with the wrong logic but I don't believe there is a way to test this otherwise. Do you have any suggestions here @t0yv0?