withTime() and withDate() methods on ZonedDateTime and PlainDateTime

[justingrant]

This PR implements a subset of the changes described in #522 (comment):

• Add PlainDateTime.withPlainDate(), PlainDateTime.withPlainTime(), ZonedDateTime.withPlainDate(), and ZonedDateTime.withPlainTime() to address the use case of combining dates and times without spreading. These methods use the 'consolidate' behaviour for calendars (throw if non-ISO and different).

This PR includes docs, polyfill implementation, docs, and TS types but not spec updates for these methods.

BTW, I found a bug in ES.ConsolidateCalendars that is fixed here. That method never worked if the second calendar was ISO.

[codecov]

Codecov Report

Merging #1181 (8ada529) into main (5930868) will decrease coverage by 2.73%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1181      +/-   ##
==========================================
- Coverage   93.55%   90.82%   -2.74%     
==========================================
  Files          19       17       -2     
  Lines        7961     9381    +1420     
  Branches     1264     1279      +15     
==========================================
+ Hits         7448     8520    +1072     
- Misses        506      851     +345     
- Partials        7       10       +3     

Flag	Coverage Δ
test262	?
tests	90.82% <ø> (+1.38%)	⬆️

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Impacted Files	Coverage Δ
polyfill/lib/shim.mjs
polyfill/lib/slots.mjs
polyfill/lib/legacydate.mjs
polyfill/lib/intrinsicclass.mjs
lib/intrinsicclass.mjs	56.81% <0.00%> (ø)
lib/plaindatetime.mjs	90.94% <0.00%> (ø)
lib/plainmonthday.mjs	84.15% <0.00%> (ø)
lib/intl.mjs	99.74% <0.00%> (ø)
lib/plaintime.mjs	87.45% <0.00%> (ø)
lib/calendar.mjs	77.68% <0.00%> (ø)
... and 11 more

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[justingrant]

All review feedback so far has been addressed. My git skills weren't good enough to keep @Ms2ger's spec commit separate so I just squashed it into the latest force-push.