test: add sarif validation

[sruehl]

relates to #1407.

This PR adds a schema validation to the tests to spot issues with wrong schema early

[sruehl]

@ccojocar can you have a look at this PR? it seems that the SARIF reports are all over the place regarding the Schema. I think the validation is vital going forward with the fixes in #1407 for example

[sruehl]

one sec, I updated this to v6 validation. For some reason I picked up v5

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.66%. Comparing base (1216c9b) to head (035fe95).
⚠️ Report is 128 commits behind head on master.
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1417      +/-   ##
==========================================
- Coverage   68.49%   64.66%   -3.84%     
==========================================
  Files          75       76       +1     
  Lines        4384     4590     +206     
==========================================
- Hits         3003     2968      -35     
- Misses       1233     1487     +254     
+ Partials      148      135      -13     

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