Add option to skip reporting when no files are changed

[andybelltree]

1. Added an option dont-post-if-no-changed-files-in-report. If this is set to true, and a report is generated with no changed files, it doesn't post a comment. This is to reduce noise (our use case is a repo with a number of projects, and we don't want a report posted about every project for every change, but we still do want the tests to run for downstream projects)
2. If an empty report is generated without this option, and no files are changed, (and filter-changed-files is set) then don't publish an empty table with a header
3. Added max-uncovered-lines option. If supplied will limit the number of uncovered lines displayed in the coverage column.
4. Added fail-drop-percent-threshold. If supplied, and doing a diff against an existing report, the gha will fail when percentage change is greater than given value. Can test it out with andybelltree/[email protected]