Add #[RunTestsInSeparateProcesses] attribute to all Functional/FunctionalJavascript tests

Problem/Motivation

Process isolation in PHPUnit 12 must be specified on each concrete test class.

Proposed resolution

In this issue, add #[RunTestsInSeparateProcesses] attribute to all Functional/FunctionalJavascript tests.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet