Adapt template sensors to use the same plural trigger/condition/action definitions as automations

[chammp]

Proposed change

This MR adapts template entities with triggers to the new plural-ish syntax used by automations starting with 2024.10. Also here the plural forms will be the default in the internal configuration view, and the old syntax is still fully compatible, and there are probably no plans to remove the legacy singular form, at least not by me 😉

So, this kind of configs are all valid (non-exhaustive list):

template:
  - trigger:
      - platform: time_pattern
        seconds: "*"
    sensor:
      - [...]

  - triggers:
      - trigger: time_pattern
        seconds: "*"
    conditions:
      - condition: state
        entity_id: input_boolean.test
        state: 'on'
    actions:
      - action: input_boolean.toggle
        target:
          entity_id: input_boolean.updated_by_template_sensor_action
    sensor:
      - [...]

I also refactored some shared constants and code to a new automation helper file. I also thought about using a common "execution definition" scheme that could be used by automations and template entities for their own schemas, but for now decided not to go down that road.

Type of change

• [ ] Dependency upgrade
• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New integration (thank you!)
• [x] 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: https://github.com/home-assistant/home-assistant.io/pull/35133

Checklist

• [x] The code change is tested and works locally.
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• [x] Tests have been added to verify that the new code works.

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

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[frenck]

Added docs-missing label, as there is no documentation PR attached that adjusts our documentation accordingly.

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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!

[chammp]

Un-Stale

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[emontnemery]

I'm happy with the PR now, but since I did some modifications a second pair of eyes would be good