Fix TS types for required CalendarProtocol methods

[justingrant]

The docs say:

The other, more difficult, way to create a custom calendar is to create a plain object implementing the Temporal.Calendar protocol, without subclassing. The object must implement all of the Temporal.Calendar properties and methods except for id, fields(), mergeFields(), and toJSON().

The TS types currently allow many CalendarProtocol methods to be undefined other than the 4 above. This PR aligns the TS types to the docs.

@sffc @ptomato holler if the docs are wrong.

[codecov]

Codecov Report

Merging #1964 (55db928) into main (f2405e1) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1964   +/-   ##
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  Coverage   95.00%   95.00%           
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  Files          19       19           
  Lines       10946    10946           
  Branches     1739     1739           
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  Hits        10399    10399           
  Misses        531      531           
  Partials       16       16           

Flag	Coverage Δ
test262	80.04% <ø> (ø)
tests	89.83% <ø> (ø)

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[ptomato]

LGTM, in order to have a fully functional plain-object calendar all these methods are required.

To be clear, you can leave them out and nothing will complain so long as you don't use any features that require them, which we do in some of our tests. But that doesn't seem like the use case that TypeScript bindings should address.