ControlNet API

[huchenlei]

Description

Closes #110.
This PR adds back API support for ControlNet.

List of things achieved in this PR

• Unittests for ControlNet API
• Add processed.extra_images to API response
• Fix the default value for many ControlNetUnit fields. The extra tailing , is making default value tuple of single item
• Add back save_detected_map API only option
• Parse ControlNet API payload

Note:
Now the only way to pass image/mask to ControlNet unit is

{
  "image": $base64string,
  "image_mask": $base64string,
  ...
}

All other syntax are no longer supported.

Screenshots/videos:

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests

[huchenlei]

Seems like inference with real SD model on CPU is too slow for ControlNet tests. Let me find a way to load empty model for tests.

[huchenlei]

Temporarily disable ControlNet tests in CQ. All tests passed locally.