Adress pytest socketblocked exception issues

[Zeitsperre]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes nimbus.fetch raises misleading error when pytest-socket is not installed #2322
  • This PR relates to ⚠️ Nightly upstream-dev CI failed ⚠️ xscen#694
• Tests for the changes have been added (for bug fixes / features)
  • (If applicable) Documentation has been added / updated (for bug fixes / features)
• CHANGELOG.rst has been updated (with summary of main changes)
  • Link to issue (:issue:number) and pull request (:pull:number) has been added

What kind of change does this PR introduce?

• Sets SocketBlockedError to a subset of the Exception class, so that if ever it is encountered while pytest-socket is not installed (e.g. in downstream libraries), it doesn't error out during failed HTTP requests

Does this PR introduce a breaking change?

No.

Other information:

This should make it so that downstream libraries do not require pytest-socket, but can still make use of it if they wish to.

Credit for this solution is owed to @aulemahal.

[Zeitsperre]

This PR needs fixes to deal with the new xsdba documentation structure. Sending along a PR soon.