Expose location for calendar events

[karwosts]

Proposed change

Expose location for calendar events. Minor CSS tweaks.

Some before and after comparisons below

Before (no description no location):

State info alignment feels off here, the gap between the state-info ("Calendar 2" and "3 days ago") seems too big, it's supposed to be lined up with the lower calendar icon but it's spilling into the area next to the upper icon?

After:

Before (location, no description):

After (the entity name and location here just happened to be the same):

Before (location & description):

After:

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 Calendar event dialog does not show or allow editing the location (the backend supports it) #27973
• This PR is related to issue or discussion:
  https://github.com/orgs/home-assistant/discussions/187
  https://github.com/orgs/home-assistant/discussions/1687
• 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

[karwosts]

Was trying to avoid here populating location key with an empty string where it wasn't previously present (I think every calendar integration supports location, but I'm not 100% sure).

But once location has a value, neither undefined or null will clear it, so we have to use empty string in that case.