Editorial: Collapse nonterminals only used for disambiguation

[ptomato]

Prefer language like "the first |TemporalDecimalFraction|, if present" rather than defining several nonterminals such as |TimeFraction|, |DurationHoursFraction|, etc.

Closes: #2006

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.57%. Comparing base (82ad54f) to head (d9d1722).
Report is 12 commits behind head on main.

❗ Current head d9d1722 differs from pull request most recent head 3765bf6

Please upload reports for the commit 3765bf6 to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2767      +/-   ##
==========================================
+ Coverage   96.51%   96.57%   +0.06%     
==========================================
  Files          23       23              
  Lines       12432    12243     -189     
  Branches     2258     2268      +10     
==========================================
- Hits        11999    11824     -175     
+ Misses        374      358      -16     
- Partials       59       61       +2     

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[gibson042]

Reviewed (in person!). I'm hoping to recover the simplicity of ParseTemporalDurationString via something like #2290, but that would build on top of this anyway.

[ptomato]

@gibson042 Thanks for finding the time to review these in person!