Calendar: filter by room

[Moliholy]

Closes #6148
Closes #6149

This PR adds the following:

• Two actions to the calendar legend: one for selecting all items and another one for deselecting them all.
• Filtering by room in the legend.

Screenshots

[Moliholy]

@ThiefMaster ready for review 😎

[ThiefMaster]

i have not really looked at the logic yet, this is just the one thing that i immediately noticed which could be shortened a bit

[Moliholy]

Rebased to the lastest master branch.

[ThiefMaster]

What do you think about using natural sort order for this list?

const collator = new Intl.Collator(undefined, {numeric: true, sensitivity: 'base'});
whatever.sort((a, b) => collator.compare(a, b));

[ThiefMaster]

I'd add the two issues and this PR to the relevant changelog entries added in the last PR, and adjust the wording there if needed

[Moliholy]

What do you think about using natural sort order for this list?

Agreed. Just applied the changes.

[Moliholy]

I'd add the two issues and this PR to the relevant changelog entries added in the last PR, and adjust the wording there if needed

Done in f3424a5.

[ThiefMaster]

• It looks rather weird when there are events with just a venue but no room
• The little triangle generally collapses/expands something, so I was rather surprised when this wasn't the case here.
• The room list in there is not using natural sorting order

[Moliholy]

It looks rather weird when there are events with just a venue but no room
The room list in there is not using natural sorting order

Both of them fixed.

The little triangle generally collapses/expands something, so I was rather surprised when this wasn't the case here.

The triangle was used initially just to visually align different elements. Ideally in a second iteration we planned to allow collapsing elements.