feat(timeline): Configurable timeline date dividers

[stefanceriu]

Expose a timeline configuration option to allow date separators to go in between different days or different months.
The only real logic change is in the first commit in DateDividerAdjuster::is_same_date_as where the configuration option is now taken into account.

This will work together with the newly added message_filtered_timeline to power the Element X media gallery and its sections.

This PR also renames all day dividers to date dividers in the last 2 commits.

[codecov]

Codecov Report

Attention: Patch coverage is 73.33333% with 28 lines in your changes missing coverage. Please review.

Project coverage is 85.24%. Comparing base (32e2070) to head (2f7a0f3).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/matrix-sdk-ui/src/timeline/date_dividers.rs	73.23%	19 Missing ⚠️
...tes/matrix-sdk-ui/src/timeline/controller/state.rs	73.33%	4 Missing ⚠️
crates/matrix-sdk-ui/src/timeline/builder.rs	0.00%	3 Missing ⚠️
...rates/matrix-sdk-ui/src/timeline/controller/mod.rs	81.81%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4398      +/-   ##
==========================================
- Coverage   85.27%   85.24%   -0.04%     
==========================================
  Files         282      282              
  Lines       31130    31149      +19     
==========================================
+ Hits        26546    26552       +6     
- Misses       4584     4597      +13     

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[andybalaam]

Looks good; a couple of light suggestions.

Make sure this doesn't get squashed when you merge since the separation you have made between renames and functional changes is really helpful.