refactor: simplify WordWrapper implementation

[tranzystorekk]

The WordWrapper implementation is a large and almost unreadable chunk of code, so I decided to do a ground-up cleaning.

Highlights and notes in no particular order:

• Before, due to extensive nesting and poor communication the control flow was foggy and mentally exhausting. Now the code is more clearly separated into a) emitting any currently cached lines (self.wrapped_lines) and b) processing the input iterator for any input to be wrapped and cached for step a
• I tried to invert and compact any larger if blocks, using let-else and labeled blocks. These features came in Rust 1.65 so they shouldn't affect our MSRV
• I attempted to rename some variables to more clearly signal intent, e.g. unfinished_word -> pending_word, has_seen_non_whitespace -> non_whitespace_previous
• Reduced the number of comments, in the old code a lot of them only contributed to the general noise or redundancy
• Some miscellaneous changes, like using u32::saturating_sub or VecDeque::drain

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 99.06542% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.4%. Comparing base (3f2f2cd) to head (76a368a). Report is 5 commits behind head on main.

Files	Patch %	Lines
src/widgets/reflow.rs	99.0%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1193 +/- ## ===================================== Coverage 94.4% 94.4% ===================================== Files 62 62 Lines 14941 15000 +59 ===================================== + Hits 14110 14169 +59 Misses 831 831 ```

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[tranzystorekk]

Went ahead and applied changes to resolve the most obvious comments

[joshka]

Thanks for the PR!