Expand use of the Problems Panel for CMakePresets errors

We have a diagnostic collection for the Problems Panel for CMakePresets validation and expansion as of #3905. This can now be extended for lots of other entry points - for example, confirming that step 1 of the workflow preset is a configure step, schema validation, etc.

It will need to be fleshed out further to make sure we don't wipe out errors when adding new ones.

Read the diagnostic collection added by #3905 and trace the CMakePresets validation and expansion entry points. Check how workflow preset step validation and schema validation report Problems Panel diagnostics, then verify that adding diagnostics preserves existing errors rather than wiping them.

Written by the indexing model from the issue text.