Tests: make dataproviders `static`

[jrfnl]

Context

*

Summary

This PR can be summarized in the following changelog entry:

• Tests: use static dataproviders

Relevant technical choices:

As of PHPUnit 10, data providers are (again) expected to be static methods.

This updates the test suite to respect that.

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• N/A If the builds pass, we're good.

[coveralls]

Pull Request Test Coverage Report for Build 6925372489

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall first build on JRF/tests-static-dataproviders at 48.608%

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Totals
Change from base Build 6925352769:	48.6%
Covered Lines:	1100
Relevant Lines:	2263

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💛 - Coveralls