Change naming of MQTT entities to correspond with HA guidelines

[jbouwh]

Breaking change

The way MQTT entities are named and how device configuration can be shared between discovered entities has changed

Sharing of device configuration

Discovered MQTT entities can share device configuration, meaning one entity can include the full device configuration and other entities can link to that device by only setting mandatory fields.
The mandatory fields were previously limited to at least one of connection and identifiers, but has now been extended to at least one of connection and identifiers as well as the name.

Naming of MQTT entities

Naming of MQTT entities has been changed to be aligned with the entity naming guidelines:

• The has_entity_name entity will be set to True on all MQTT entities
• This means any MQTT entity which is part of a device will automatically have it's friendly_name attribute prefixed with the device name
• Unnamed binary_sensor, button, number and sensor entities will now be named by their device class instead of being named "MQTT binary sensor" etc.
• It's now allowed to set an MQTT entity's name to None to mark it as the main feature of a device

Proposed change

Change naming of MQTT entities to better correspond with the current guidelines in https://developers.home-assistant.io/docs/core/entity/#entity-naming

Always set the has_entity_name attribute on MQTT entities to True.

If a device_class is set and the entity name is not set, it follows the device class name.
The changed behavior for the generation the default entity_id is documented in the linked docs PR.

The name and in MQTT entity can now also explicitly be set to None (or null in a JSON discovery payload).
This will avoid inherit the device name as friendly name.

Link blog post PR: home-assistant/developers.home-assistant#1851

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: Changes in naming of MQTT entities home-assistant.io#27954

Checklist

• The code change is tested and works locally.
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• 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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[home-assistant]

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

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[emontnemery]

Thanks @jbouwh 👍