Clean up unused directories under `jobs` on the jenkins server

Extracted from https://github.com/adoptium/infrastructure/issues/2108#issuecomment-1469958569

We have a lot of jobs not in the UI but are on the file system. This seems to be because the config.xml has gone but the job directory is still present (Maybe due to artefacts being kept after job deletion?). These can be identified with `for A in *; do if [ ! -r $A/config.xml ]; then ls -ld $A; fi; done` in the `jobs` directory - at the time of writing there are 1695 without a config.xml (directly under jobs) of which all but 195 are Test_openjdk ones.

897 of these are @script directories as opposed to job directories that mostly contain extracted copies of openjdk-tests (Now an obsolete name). Of the 2736 @script ones, 689 have a corresponding job named the same, so over 200 do not. Only one of those 689 (Grinder_perf) is missing a config.xml.

There are also 15 `@tmp` suffixed directories and six `@libs`

None of the analysis above covers anythign that might be in subfolders.

I suspect we should clean up all of the `@script` directories (The most recently updated one was from 2021) and also have a backup/purge on all other directories without a config.xml

Start with the extracted discussion in infrastructure issue 2108 and inspect the Jenkins jobs directory using the provided config.xml check. Review the @script, @tmp, @libs, and other directories lacking config.xml, including possible subfolders. Done means agreeing on backup and purge scope and cleaning the obsolete directories without removing active jobs.

Written by the indexing model from the issue text.