feat(push): add experimental support for applying "Do not Disturb" notification settings as per MSC4359

[Johennes]

This adds partial support for matrix-org/matrix-spec-proposals#4359 and suppresses push notifications when a room is set to "Do not Disturb" (DnD). The DnD setting is sourced from a dedicated global account data event.

• Public API changes documented in changelogs (optional)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.40%. Comparing base (943b048) to head (1292755).
⚠️ Report is 1464 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5687   +/-   ##
=======================================
  Coverage   88.40%   88.40%           
=======================================
  Files         359      359           
  Lines       99060    99063    +3     
  Branches    99060    99063    +3     
=======================================
+ Hits        87570    87573    +3     
+ Misses       7353     7351    -2     
- Partials     4137     4139    +2     

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[codspeed-hq]

CodSpeed Performance Report

Merging #5687 will not alter performance

_{Comparing Johennes:johannes/msc4359 (1292755) with main (bbeb2d2)}

Summary

✅ 50 untouched

[bnjbvr]

Hi @Johennes, thanks for the contribution! I'm not against it in principle, but we're a bit concerned that adding support for experimental features like this adds significantly to the maintenance overhead of matrix-rust-sdk, and as such feel like it's probably a bit early to merge support for this into mainline, even when guarded by feature flags. Perhaps you could keep it in a fork for now, and we can revisit once the MSC (or the other) gets a bit more traction?

[Johennes]

Oh. 😯 This actually seemed relatively minimal to me, especially when compared to its predecessor #5441. I understand the rationale though and keeping this in a fork is fine. If it's ok, I'll leave this pull request open in draft state because it's currently the only public implementation of the MSC.