Breaking change

#54865 secured that homeassistant.log was backed up, by using .rotate() however it has the side effect that logging continues in the new file.
Go back to the original #54865 and use .doRollover() this renames homeassistant.log to homeassistant.log.1 and open a new file homeassistant.log

This means that homeassistant.log is the current (active/open) log, and homeassistant.log.1 is from last start of hass.

If log_rotate_days us used there will be multiple files (.1 .2 ... until log_rotate_days) each log will be either a midnight change or a start of hass.

Proposed change

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

Additional information

With 2021.8.8 homeasistant.log is effectively homeassistant.previous.log !!

• This PR fixes or closes issue: fixes #
  fixes #55144
• 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.

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