Add "power outage memory" config entity to Xiaomi EU plugs to ZHA

[TheJulianJES]

Proposed change

This adds a "Power outage memory" config entity for Xiaomi EU plugs to ZHA.
In order for this entity to show up, a new zhaquirks version with the following PR will need to be published and updated to in HA:

• Fix power measurement for Aqara MAEU01 plugs with newer firmware zigpy/zha-device-handlers#1656
• Bump ZHA quirks to 0.0.83 #80489

The only thing I wasn't completely sure about is whether or not power_outage_memory should allow a cached read in ZCL_INIT_ATTRS. I guess there's no need to re-read this attribute on startup, hence I allowed cached reads.

Example of the config entity:

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)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

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.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[home-assistant]

Hey there @dmulcahey, @Adminiuga, @puddly, mind taking a look at this pull request as it has been labeled with an integration (zha) you are listed as a code owner for? Thanks!