Add 'last_reset' for 'total' state_class template sensor

[RoboMagus]

Proposed change

Users are able to configure the state_class to be total for template sensors, but currently do not have the option to add a last_reset to this configuration. For e.g. sensors that do have a periodic reset, but may not be monotonically increasing this is a missing feature when properly trying to track statistics.

This PR aims to fix that.

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: TO-DO
• Link to documentation pull request: Add last_reset to template sensor home-assistant.io#29082

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
• I have followed the perfect PR recommendations
• 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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[home-assistant]

Hey there @PhracturedBlue, @tetienne, @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (template) you are listed as a code owner for? Thanks!

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[github-actions]

There hasn't been any activity on this pull request recently. This pull request has been automatically marked as stale because of that and will be closed if no further activity occurs within 7 days.
If you are the author of this PR, please leave a comment if you want to keep it open. Also, please rebase your PR onto the latest dev branch to ensure that it's up to date with the latest changes.
Thank you for your contribution!

[RoboMagus]

Would still like to see this integrated :)

[RoboMagus]

@PhracturedBlue, @tetienne, Mind taking a look?
The documentation PR was approved already a couple of months ago.

[emontnemery]

LGTM, thanks @RoboMagus 👍

[emontnemery]

(Close open to force CI to re-run)