refactor(widgets): remove unnecessary dynamic dispatch and heap allocation

[rhysd]

This PR refactors implementation of Paragraph::render. It allocates LineComposer trait object on heap memory and calls its methods via dynamic dispatch. However it can be easily changed to static dispatch with allocating the object on stack.

This PR does the change as refactoring. No rendering logic has changed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1e2f0be) 90.5% compared to head (3f76164) 90.5%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #597   +/-   ##
=====================================
  Coverage   90.5%   90.5%           
=====================================
  Files         41      41           
  Lines      11978   11980    +2     
=====================================
+ Hits       10850   10853    +3     
+ Misses      1128    1127    -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[joshka]

I'm a big fan of anything that simplifies complexity like this.
I can merge as-is and apply my nit after if you don't have time to make the suggested change.

[joshka]

Thanks for the PR and the requested fixes :)