Collapse grammar nonterminals that are only distinct for the purposes of disambiguation

[ptomato]

@gibson042 pointed out that we don't need to have separate nonterminals such as TimeZoneNumericUTCOffset and TimeZoneUTCOffsetName in order to disambiguate in cases such as #1796. We can refer to things like "the first |FractionalPart|, if present", cf. https://tc39.es/ecma262/multipage/ecmascript-language-statements-and-declarations.html#sec-runtime-semantics-forloopevaluation

[gibson042]

Related improvements are also possible with nonterminal parameterization, e.g.

       TimeZoneNumericUTCOffset :
-          TimeZoneUTCOffsetSign TimeZoneUTCOffsetHour
-          TimeZoneUTCOffsetSign TimeZoneUTCOffsetHour `:` TimeZoneUTCOffsetMinute
-          TimeZoneUTCOffsetSign TimeZoneUTCOffsetHour TimeZoneUTCOffsetMinute
-          TimeZoneUTCOffsetSign TimeZoneUTCOffsetHour `:` TimeZoneUTCOffsetMinute `:` TimeZoneUTCOffsetSecond TimeZoneUTCOffsetFraction? 
-          TimeZoneUTCOffsetSign TimeZoneUTCOffsetHour TimeZoneUTCOffsetMinute TimeZoneUTCOffsetSecond TimeZoneUTCOffsetFraction?
+          Sign HourComponents[+Extended]?
+          Sign HourComponents[~Extended]?
+
+      HourComponents[Extended] :
+          Hour
+          Hour TimeSeparator[?Extended] Minute
+          Hour TimeSeparator[?Extended] Minute TimeSeparator[?Extended] Second Fraction?
+
+      TimeSeparator[Extended] :
+          [+Extended] `:`
+          [~Extended] [empty]

[justingrant]

Offset grammar will be different between ISO string offsets and offset time zone identifiers after the minutes PR is merged. Does that change any of the simplifications planned here?

[gibson042]

Not really; UTCOffset nonterminals are now distinct for a legitimate reason and already incorporate parameterization as appropriate. But I still think some improvements are possible with respect to e.g. |TimeHour|/|TimeMinute|/|TimeFraction|/|TimeSpec| and the Duration productions.