[META] Deprecate non-static random generation methods from RandomGeneratorTrait

Problem/Motivation

In #3353658: [PHPUnit 10] Provide a static alternative to randomMachineName() and implement in data providers, we introduced new static methods for random data generation in tests.

In this issue, we explore whether deprecating the non-static methods, contained in RandomGeneratorTrait, for later removal.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet