[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 InteractionDataTrait to handle limited validation of the InteractionData parameter.
• Add tests for new submit methods.
• Add TestHelperTrait to 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