Backport of #48849. Update `.editorconfig` to make the Java settings the
default for all files, and then apply a 2-space indent to all `*.gradle`
files. Then reformat all the files.
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.
Rory Hunter
Nik Everett
Alpar Torok
Jason Tedor