feat(table): accept Into<Constraint> for widths

[joshka]

This allows Table constructors to accept any type that implements
Into instead of just AsRef. This is useful when
you want to specify a fixed size for a table columns, but don't want to
explicitly create a Constraint::Length yourself.

Table::new(rows, [1,2,3])
Table::default().widths([1,2,3])

---

PR includes #744 - merge that first

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (659460e) 92.3% compared to head (bb73aa2) 92.3%.
Report is 2 commits behind head on main.

❗ Current head bb73aa2 differs from pull request most recent head 46c62e1. Consider uploading reports for the commit 46c62e1 to get more accurate results

Files	Patch %	Lines
src/layout/constraint.rs	50.0%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #745     +/-   ##
=======================================
- Coverage   92.3%   92.3%   -0.1%     
=======================================
  Files         52      52             
  Lines      14806   14811      +5     
=======================================
+ Hits       13672   13674      +2     
- Misses      1134    1137      +3     

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