Remove work arounds for 10.0.x support

Problem/Motivation

Error::logException() is not available in 10.0.x. We can't easily use watchdog_exception because of the core conversion.

So we have \Drupal\package_manager\Error class

We want to be compatible with 10.0.x so people can test it with it because otherwise you cannot test doing a minor update.

Steps to reproduce

Proposed resolution

Either when 10.0.x because unsupported or when we need to merge into core we should remove these.

If 10.0.x becomes unsupported and for whatever reason we are still blocked for getting into core we may want to continue to postpone this issue so users can use the contrib module to update from the unsupported version of core. But hopefully that won't be the case and we can evaluate at that time.

Remaining tasks

User interface changes

API changes

Data model changes