Add 'focus' option to geo_location_sources for map card

[karwosts]

Proposed change

Map card entities have the focus option to exclude them from the auto-fit boundary, but geo_location_sources have no such option (so the fitBounds always wraps the entirety of all geo_location entities).

This PR adds the same focus option to geo_location_sources. As it is somewhat advanced (and not trivial to create UI for), the use of this option locks the card to yaml-only.

Can document on approval.

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 #
• This PR is related to issue or discussion: https://community.home-assistant.io/t/map-card-force-the-home-as-the-center/786623/2
• 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