[PHP] Add MetricsClient#submitInteraction()
Update the PHP client to include preliminary core interactions:
- Add base interaction submit and submitClick() methods to the Metrics Client.
- Add
InteractionDataTraitto handle limited validation of the InteractionData parameter. - Add tests for new submit methods.
- Add
TestHelperTraitto DRY tests. - Update composer to autoload tests.
- Rename/add schema constants.
Note: the monoschema contains a "name" key while the base interactions schema uses "action" in lieu of "name".
Bug: T346286