Fix PR annotations when CodeQL finds error on a single line

The GHAzDO alerts APIs can return back a lineEnd of 0 when the finding occurs on a single line:

 "region": {
    "lineStart": 71,
    "lineEnd": 0,
    "columnStart": 52,
    "columnEnd": 57,
    "snippet": "",
    "highlightSnippet": ""
}

This PR adds a small fix to detect lineEnd=0 and replace it with the lineStart so that annotations properly show up on PRs.

Error Handling Improvements:

src/pr-gating/CIGate.ps1: Added a retry mechanism to the process of fetching alerts from the target branch. This ensures that if the CodeQL scanning of the target branch (which runs in a separate task) is not yet complete, the script will attempt to fetch the results up to 10 times with a 1-minute wait between each try. If the maximum number of retries is reached or an unexpected error occurs, an error message is logged and the exception is thrown.

microsoft / GHAzDO-Resources