This commit includes breaking changes, see the change record for more info: https://www.drupal.org/node/2836073

Enforce result and reports and added plugin incoming event
Fixed failing tests
Added results and reports for incoming messages created in tests.
Added createMessageResult test helper to create reports and result for a message.
Fixed failing tests due to missing reports
Test coverage for new result/report exceptions
Compacted sms_test_gateway gateway config schema (Derivative types)
Added plugin incoming method to execution order tests.
New test file covering \Drupal\sms\EventSubscriber\SmsMessageProcessor (some \Drupal\Tests\sms\Kernel\SmsFrameworkProviderTest tests should be moved there)
Added supports incoming messages gateway annotation property.
Added SmsGateway::supportsIncoming()
Add preprocess check to incoming messages ensuring they have a gateway set, and the gateway supports incoming messages.
Added tests for above.
Added missing gateway entity to incoming message tests.

Message direction is automatically set if SmsProvider send or incoming methods.
Added new exception: \Drupal\sms\Exception\SmsDirectionException
An exception is thrown if message direction is missing when passed to SmsProvider::queue

Fixed dpi/smsframework#65

Introduces test utility methods for a incoming message storage buffer, similar to the pre-existing outgoing message buffer.

Fixed dpi/smsframework#64

Includes tests for validation exception messages.

It did not get removed with https://www.drupal.org/node/2788473 because it was named incorrectly

Removed submodules which no longer exist.
Updated information regarding hooks, which changed to events.