feat(neon_talk): Support adding and removing reactions

[provokateurin]

Closes #2037
The added patch is the equivalent of nextcloud/spreed#12386
I know adding the reactions button to every message is a bit ugly, but I will fix that properly with #2038 when a proper menu is introduced.

[codecov]

Codecov Report

Attention: Patch coverage is 80.43478% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 29.84%. Comparing base (766e775) to head (d48d8e4).
Report is 3 commits behind head on main.

❗ Current head d48d8e4 differs from pull request most recent head 2a2eeee

Please upload reports for the commit 2a2eeee to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2063      +/-   ##
==========================================
+ Coverage   29.49%   29.84%   +0.34%     
==========================================
  Files         254      254              
  Lines       84690    84774      +84     
==========================================
+ Hits        24983    25302     +319     
+ Misses      59707    59472     -235     

Flag	Coverage Δ		*Carryforward flag
cookie_store	90.51% <ø> (ø)		Carriedforward from ec9c6aa
dynamite	31.00% <ø> (ø)		Carriedforward from ec9c6aa
dynamite_end_to_end_test	61.47% <ø> (ø)		Carriedforward from ec9c6aa
dynamite_runtime	85.40% <ø> (ø)		Carriedforward from ec9c6aa
neon_dashboard	92.56% <ø> (ø)
neon_framework	39.94% <ø> (ø)
neon_talk	96.77% <100.00%> (+0.29%)	⬆️
nextcloud	26.48% <30.76%> (+0.35%)	⬆️
sort_box	90.90% <ø> (ø)		Carriedforward from ec9c6aa

*This pull request uses carry forward flags. Click here to find out more.

Files	Coverage Δ
packages/neon/neon_talk/lib/src/blocs/room.dart	97.67% <100.00%> (+1.08%)	⬆️
...ckages/neon/neon_talk/lib/src/widgets/message.dart	100.00% <100.00%> (ø)
...ages/neon/neon_talk/lib/src/widgets/reactions.dart	100.00% <100.00%> (ø)
packages/nextcloud/lib/src/api/spreed.openapi.dart	29.24% <ø> (+1.14%)	⬆️
...ckages/nextcloud/lib/src/api/spreed.openapi.g.dart	13.24% <30.76%> (+0.76%)	⬆️

[provokateurin]

Ah I forgot to add tests for the bloc part (but everything else can be reviewed already).