Improvements to /exclude workflow

Finding a few things that will improve the exclude workflow, https://github.com/adoptium/aqa-tests/blob/master/.github/workflows/autoTestPR.yml

- Consider improving the name of the workflow yml file so when trying to find it in .github/workflows, it is more obvious and related to what one might expect, autoTestPR.yml previously existed and also contains other logic, does it make sense to separate it
- Fix doc https://github.com/adoptium/aqa-tests/blob/master/docs/pages/userGuide.md#automatically-exclude-openjdk-test-cases-from-problemlist-files to point at correct reference doc (not openjdk_tests, but rather https://github.com/adoptium/aqa-tests/blob/master/openjdk/README.md#exclude-a-testcase).
- Attempt to insert the excluded testcases into the correct section of the ProblemList file, rather than appending to the end of the file (which can be the fallback behaviour if correct section can not be found).