Allow area, device, and entity selectors to optionally support multiple selections like target selector

[r-t-s]

Proposed change

Changes to the Area, Device, and Entity selectors to allow them to select multiple entities.
The user interface is similar to the Area, Device and Entity selector component of the target selector.
Single or multi select is configured with the optional multiple option on the selector configuration.
The selectors can now potentially return a list of area, device, or entity IDs.

This is motivated by the need to have multiple entity selector so a blueprint can trigger on multiple entities.
But brings a consistent UI for the Area, Device, Entity, and Target selector.

Type of change

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

Example configuration

blueprint:
  name: Test Selectors
  description: This is used to test the variois Selectors
  domain: automation
  source_url: https://github.com/home-assistant/core/blob/dev/homeassistant/components/automation/blueprints/test.yaml
  input:
    target_selector:
      name: My Target Selector
      selector:
        target:
    entity_selector:
      name: My Entity Selector
      selector:
        entity:
          multiple: True
    area_selector:
      name: My Area Selector
      selector:
        area:
          multiple: True
          device:
            model: Forecast
    device_selector:
      name: My Device Selector
      selector:
        device:
          multiple: True

mode: single
max_exceeded: silent

trigger:
  platform: state
  entity_id: !input entity_selector

action:
    delay: 30

Additional information

Associated core PR #63138

• This PR fixes or closes issue: fixes #
• This PR is related to issue or discussion:
• Link to documentation pull request: #20961

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• 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

[balloob]

this code needs to be generalized. This is now copy pasted 3 times?

I think it might benefit it we start with a single selector in this PR instead of trying to do entity, device and areas in one PR.

[r-t-s]

How about a single selector file with a common base class and 4 specializations (Target, Area, Device, Entity) ?
Then we have the existing Area, Device and Entity pickers that are called from the selectors.

[r-t-s]

When I noticed the merge conflicts I also noticed that much of the work of this PULL request has already been completed.
i.e. the selection support for multiple Entities, Areas, and Devices.
One difference is that this PULL request tried to unify the style of the UI for Target, Area, Entity, and Device selectors.
Should I continue this effort or NOT ?

[zsarnett]

PRobably be easier to start from scratch with the new code. This is something we want to do eventually so if you would like to do these one at a time then that would be great!

[balloob]

So one thing we have been considering (but didn't get to) is to unify the look of targets, area, device and entity picker to all look like targets. That would be something to pursue.