Removing 'source results only' logic from PR scan

[eranturgeman]

• All tests passed. If this feature is not already covered by the tests, I added new tests.
• This pull request is on the dev branch.
• I used gofmt for formatting the code before submitting the pull request.
• Update documentation about new features / new supported technologies

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This PR simplifies the auditPullRequestSourceCode func and better handling target results lacking issue.
We remove the case where we enable the target results to be absent, since in the new flow we only performing a diff scan, therefore:

1. if targetBranchWd is empty or there are no target results - there was an issue with the scan
2. if both exists as they should - we always add the targetWd path to the scanResultsToIssuesCollection func

[github-actions]

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