feat(line): impl Styled for Line

[joshka]

This adds FromIterator impls for Line and Text that allow creating
Line and Text instances from iterators of Span and Line
instances, respectively.

let line = Line::from_iter(vec!["Hello".blue(), " world!".green()]);
let line: Line = iter::once("Hello".blue())
    .chain(iter::once(" world!".green()))
    .collect();
let text = Text::from_iter(vec!["The first line", "The second line"]);
let text: Text = iter::once("The first line")
    .chain(iter::once("The second line"))
    .collect();

[joshka]

Includes #967 - merge that first for separate changelog entries.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.7%. Comparing base (943c043) to head (bf1ed9b).

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #968   +/-   ##
=====================================
  Coverage   91.7%   91.7%           
=====================================
  Files         61      61           
  Lines      15742   15809   +67     
=====================================
+ Hits       14440   14507   +67     
  Misses      1302    1302           

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