fix: use fully qualified global namespaces when referencing internal classes

[jupjohn]

Description

This PR aims to fix compilation errors when doing source gen inside of a Cluster namespace. Fixes #1840

I'm leaving this as a draft until I can get home and resign my commits with my PGP key.

Purpose

This pull request is a:

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

I don't believe the following need to be done for this as functionality will be confirmed by existing tests.

• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[CLAassistant]

All committers have signed the CLA.

[jupjohn]

There's another issue I found indirectly referencing the usage of global:: fully qualified namespaces (after I submitted my own) but I can't for the life of me find it now. If anyone managed to find it, it could probably be closed off too :)