Regression for attribute's format in entities card

[mbo18]

Checklist

• I have updated to the latest available Home Assistant version.
• I have cleared the cache of my browser.
• I have tried a different browser to see if it is related to my browser.

Describe the issue you are experiencing

format for type:attribute seems to be no more supported by the visual editor for entities card.

format is in the documentation for attribute, see: https://www.home-assistant.io/lovelace/entities/#attribute

Describe the behavior you expected

format should be valid and should not raise an error in the editor (works fine when editing raw config)

Steps to reproduce the issue

1. edit or add an entities card
2. add an attribute:

entities:
  - type: attribute
    entity: sun.sun
    attribute: next_rising
    name: Levé du soleil

3. add format to it:

entities:
  - type: attribute
    entity: sun.sun
    attribute: next_rising
    name: Levé du soleil
    format: datetime

editor then display a lot of errors:

Configuration errors detected:

Required key "entities.0.tap_action" is missing.
Required key "entities.0.tap_action" is missing.
Required key "entities.0.tap_action" is missing.
Required key "entities.0.tap_action" is missing.
Required key "entities.0.tap_action" is missing.
Required key "entities.0.tap_action" is missing.
Required key "entities.0.view" is missing.
Required key "entities.0.view" is missing.
Required key "entities.0.view" is missing.
Required key "entities.0.conditions" is missing.
Required key "entities.0.url" is missing.
Required key "entities.0.entities" is missing.
Required key "entities.0.service" is missing.
Required key "entities.0.text" is missing.
Required key "entities.1.tap_action" is missing.
Required key "entities.1.tap_action" is missing.
Required key "entities.1.tap_action" is missing.
Required key "entities.1.tap_action" is missing.
Required key "entities.1.tap_action" is missing.
...

What version of Home Assistant Core has the issue?

core-2021.9.3

What was the last working version of Home Assistant Core?

No response

In which browser are you experiencing the issue with?

Firefox and Safari latest release

Which operating system are you using to run this browser?

macOS Catalina

State of relevant entities

No response

Problem-relevant frontend configuration

entities:
  - type: attribute
    entity: sun.sun
    attribute: next_rising
    name: Levé du soleil
    format: datetime

Javascript errors shown in your browser console/inspector

No response

Additional information

Could you also add support for icon: for type:attribute?

It works when editing raw config but is not supported by the visual editor. See: #9959 or #9586