In #29623 we added `Request` object flavored requests to the low level
REST client and in #30315 we deprecated the old `performRequest`s. This
changes all calls in the `x-pack/qa/audit-tests`,
`x-pack/qa/ml-disabled`, and `x-pack/qa/multi-node` projects to use the
new versions.
This commit moves the ML QA tests to be a sub-project of ML. The purpose
of this refactoring is to enable ML developers to run
:x-pack:plugin:ml:check and run the vast majority of a ML tests with a
single command (this still does not contain the ML REST tests, nor the
upgrade tests). This simplifies local development for faster iteration.