Add feature flag to skip computing baseline file coverage information on PRs #835

Job	Run time
Test different uses of `upload-sarif` (ubuntu-latest, default, code-scanning,code-quality)	3m 49s
Test different uses of `upload-sarif` (ubuntu-latest, default, code-quality)	3m 20s
Test different uses of `upload-sarif` (ubuntu-latest, default, code-scanning)	3m 27s
	10m 36s

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