Support/wagtail upgrades (Wagtail <= 5.2)

[katdom13]

Wagtail 5.2 release notes

Changes

• Update test matrices
• Drop tests for Wagtail 4.2 and 5.0 as they have reached EOL

This PR combines the following along with the latest upgrades:

• Wagtail 4.x - 5.0
• Wagtail 5.1

[pflynny]

@katdom13 thanks for your work on this! I’ve just tested it, and everything is working as expected.

We’ll be making some additional updates to this package soon, this is a great step forward.