Update TS types of TimeZone-like/Calendar-like params to match spec and polyfill

[justingrant]

Extends TS tsupport for property-bag form of Calendar-like and TimeZone-like params in Temporal methods. Fixes #118

Also allows Temporal.Calendar instances to be used in the Intl.DateTimeFormatOptions type. (Previously only string IDs were allowed.) Fixes #124.

Note that fixing tc39/proposal-temporal#2005 will further extend the types that can be passed into the calendar and timeZone properties of Intl.DateTimeFormatOptions. But that requires a spec change and polyfill code change, so in this PR we'll only extend Intl.DateTimeFormatOptions to what's supported by the current spec and polyfill.

[ptomato]

LGTM, a couple of questions though:

• Update type declarations for "Timezone-like" and "Calendar-like" parameters to support ZDT property bags #118 mentions removing a cast: https://github.com/js-temporal/temporal-polyfill/pull/109/files#r779978091, should that be part of this PR?
• does this encode the "no recursive property bags" rule or is that coming in a follow-up?

[justingrant]

• Update type declarations for "Timezone-like" and "Calendar-like" parameters to support ZDT property bags #118 mentions removing a cast: https://github.com/js-temporal/temporal-polyfill/pull/109/files#r779978091, should that be part of this PR?

Good catch! Thanks for remembering that. Fixed now in latest commit. (Both the timezone and the calendar cast could be removed.)

• does this encode the "no recursive property bags" rule or is that coming in a follow-up?

I couldn't figure out how to encode that in TS types. Tried a few ways to do it, none of them seemed to work. So leaving that for someone with better TypeScript Fu than me.

[ptomato]

leaving that for someone with better TypeScript Fu than me.

Well, certainly not me. I salute whoever it is!

[justingrant]

• does this encode the "no recursive property bags" rule or is that coming in a follow-up?

I couldn't figure out how to encode that in TS types. Tried a few ways to do it, none of them seemed to work. So leaving that for someone with better TypeScript Fu than me.

Actually, I take that back. If an object bag is used, then its timeZone or calendar property, respectively, must be string | TimeZoneProtocol or string | CalendarProtocol. The two protocol types already have timeZone?: never and calendar?: never properties defined which should disallow recursion. It's not perfect; a timeZone: undefined property will pass TS, but any non-undefined value will cause a compile error. I tried making those never properties non-optional, but this broke other code so I figured we can just take the W with the current types.