Convert customize to LitElement + "real" entity picker + option to directly jump to entity

[spacegaier]

Breaking change

Proposed change

Converted parts of the customize section to LitElement. Two changes compared to before:

1. Proper entity picker is now used so keyboard search strings work
2. Option added to directly jump to an entity via the URL: /config/customize/edit/climate.bath. In a separate PR I will make use of that to offer an easy navigation from the entity more info.

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

Additional information

• This PR fixes or closes issue: fixes Add ability to search for entity_id to customize UI #4351
• This PR is related to issue or discussion:
• Link to documentation pull request:

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