fix(neon_rich_text): Do not inherit the current TextStyle in rich objects

[provokateurin]

Extracted from #2647

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 28.89%. Comparing base (1e4928e) to head (ebbe458).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2701      +/-   ##
==========================================
- Coverage   28.89%   28.89%   -0.01%     
==========================================
  Files         373      373              
  Lines      136630   136625       -5     
==========================================
- Hits        39481    39476       -5     
  Misses      97149    97149              

Flag	Coverage Δ		*Carryforward flag
account_repository	98.47% <ø> (ø)
cookie_store	99.48% <ø> (ø)		Carriedforward from 1e4928e
dashboard_app	96.05% <ø> (ø)
dynamite	31.05% <ø> (ø)		Carriedforward from 1e4928e
dynamite_end_to_end_test	61.69% <ø> (ø)		Carriedforward from 1e4928e
dynamite_runtime	85.40% <ø> (ø)		Carriedforward from 1e4928e
interceptor_http_client	97.18% <ø> (ø)		Carriedforward from 1e4928e
neon_dashboard	96.05% <ø> (ø)		Carriedforward from 1e4928e
neon_framework	59.25% <ø> (ø)
neon_http_client	93.61% <ø> (ø)		Carriedforward from 1e4928e
neon_notifications	100.00% <ø> (ø)		Carriedforward from 1e4928e
neon_rich_text	100.00% <100.00%> (ø)
neon_storage	94.66% <ø> (ø)		Carriedforward from 1e4928e
neon_talk	99.45% <ø> (ø)		Carriedforward from 1e4928e
nextcloud	24.33% <ø> (ø)		Carriedforward from 1e4928e
notifications_app	97.43% <ø> (ø)
notifications_push_repository	98.11% <ø> (ø)
sort_box	90.90% <ø> (ø)		Carriedforward from 1e4928e
talk_app	98.82% <ø> (ø)

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

Files with missing lines	Coverage Δ
.../neon_rich_text/lib/src/rich_objects/fallback.dart	100.00% <100.00%> (ø)
...ages/neon_rich_text/lib/src/rich_objects/file.dart	100.00% <100.00%> (ø)
...s/neon_rich_text/lib/src/rich_objects/mention.dart	100.00% <ø> (ø)
...n_rich_text/lib/src/rich_objects/rich_objects.dart	100.00% <ø> (ø)