Swarming: Adds CountTasks endpoint & Refactors swarming Prpc request

[IvanBM18]

As part of the Swarming backpressure initiative, we needed to launch request to the prpc's swarming.v2.Task/CountTasks endpoint to achieve this i moved the logic prpc logic to its own module to reuse code and keep responsibilities in separate files.

Changes

• Created a new api.py file in the swarming module.
  • Moved the request logic from __init__.py to api.py
  • Created a new class SwarmingAPI to handle the prpc request logic such as token/auth logic, swarming config handling, and any other request logic
• Created new unit tests for this api and Updated existing unit tests.

Tests

• Created unit tests for the new api & endpoint
• Scheduled swarming jobs to verify that the refactor didn't broke the existing swarming logic

Note:

This PR is dependendant to this other PR any changes you see related to the proto files are to be reviewed in said pr.