Migrate WLED to use DataUpdateCoordinator

[frenck]

Proposed change

Migrate the WLED integration to use the DataUpdateCoordinator, and refactored anything that can leverage that more efficient in the process.

Tests have been adjusted and have a 100% coverage.

----------- coverage: platform linux, python 3.7.6-final-0 -----------
Name                                           Stmts   Miss  Cover
------------------------------------------------------------------
homeassistant/components/wled/__init__.py         92      0   100%
homeassistant/components/wled/config_flow.py      56      0   100%
homeassistant/components/wled/const.py            20      0   100%
homeassistant/components/wled/light.py            92      0   100%
homeassistant/components/wled/sensor.py           51      0   100%
homeassistant/components/wled/switch.py           66      0   100%
------------------------------------------------------------------
TOTAL                                            377      0   100%

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example entry for configuration.yaml:

# Example configuration.yaml

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

The integration reached or maintains the following Integration Quality Scale:

• No score or internal
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• 🥇 Gold
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[MartinHjelmare]

Very nice!