Fix is_user_mention_enabled and is_room_mention_enabled

[nimau]

With this PR:

• is_user_mention_enabled() now returns the value of the new push rule .m.rule.is_user_mention if the rule exists. Previously, the value of the new push rule was only returned if it was enabled.
• is_room_mention_enabled() now returns the value of the new push rule .m.rule.is_room_mention if the rule exists. Previously, the value of the new push rule was only returned if it was enabled.

The previous implementation was problematic because setting is_room_mention_enabled() to false actually makes 2 API calls:

• One disabling the new push rule .m.rule.is_room_mention
• One disabling the deprecated rule .m.rule.roomnotif

And the client app was seeing the room mention enabled after the first call because the previous implementation was returning the state of the deprecated rule if the new one was disabled.
In this way, the new push rule is the one used if it exists.

This PR also fixes some UnitTests for notification_settings crate.

[codecov]

Codecov Report

Patch coverage: 85.34% and project coverage change: +0.03% 🎉

Comparison is base (4c7e10c) 77.57% compared to head (6071a39) 77.61%.
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2357      +/-   ##
==========================================
+ Coverage   77.57%   77.61%   +0.03%     
==========================================
  Files         175      175              
  Lines       18471    18536      +65     
==========================================
+ Hits        14329    14386      +57     
- Misses       4142     4150       +8     

Files Changed	Coverage Δ
crates/matrix-sdk-crypto/src/gossiping/machine.rs	63.58% <ø> (ø)
crates/matrix-sdk-crypto/src/lib.rs	100.00% <ø> (ø)
crates/matrix-sdk-crypto/src/requests.rs	78.66% <ø> (ø)
crates/matrix-sdk-crypto/src/store/mod.rs	78.30% <33.33%> (-1.10%)	⬇️
crates/matrix-sdk-sqlite/src/crypto_store.rs	93.33% <33.33%> (-0.94%)	⬇️
crates/matrix-sdk/src/room/mod.rs	76.12% <75.00%> (+0.22%)	⬆️
crates/matrix-sdk-ui/src/timeline/inner/state.rs	89.40% <81.81%> (+2.87%)	⬆️
crates/matrix-sdk-base/src/client.rs	88.46% <87.50%> (-0.07%)	⬇️
crates/matrix-sdk-base/src/sliding_sync.rs	86.54% <87.50%> (+0.24%)	⬆️
crates/matrix-sdk-ui/src/notification_client.rs	68.88% <92.30%> (+2.41%)	⬆️
... and 10 more

... and 3 files with indirect coverage changes

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[bnjbvr]

Sweet! We could use a test helper, and then this would be good to go 👍