[Feature] Move SelectedTests into TestRunExecutionCreate

[antonio-amjr]

Feature description

Providing the SelectedTests to create a new TestRunExecution is now mandatory.
So would be convenient to include this information to the TestRunExecutionCreate schema, but that would require to also change the TestRunExecution model since the schema is used in the model creation.
This also require to change the way Frontend create JSON Request Data for the endpoint.

Also analyze if this portion of the code crud_test_run_execution.py#L188-L194 could be moved to TestRunner or somewhere else.

Use Cases

[Use Case] Create a TestRunExecution:

• Create a json including all data to TestRunExecution plus the SelectedTests in Frontend
• Use the create TestRunExecution endpoint of Backend providing the json data

Test Cases

No response

Additional Information

This is a spin-off issue from Backend PR#16.

[fabiowmm]

Deprioritized.