handling of 'islamic' and 'islamic-rgsa' calendars

[fabon-f]

As far as I understand, there is a consensus that Temporal doesn't accept nor do fallback for 'islamic' and 'islamic-rgsa' calendars, as specified in tc39/proposal-intl-era-monthcode#46 . But currently temporal_rs accepts these calendars, and I believe this is spec-incompliant.

temporal/src/builtins/core/calendar.rs

Lines 144 to 159 in d125b62

	let icu_locale_value = Value::try_from_utf8(&bytes.to_ascii_lowercase())
	.map_err(|e| TemporalError::range().with_message(e.to_string()))?;
	let algorithm = CalendarAlgorithm::try_from(&icu_locale_value)
	.map_err(|e| TemporalError::range().with_message(e.to_string()))?;
	let calendar_kind = match AnyCalendarKind::try_from(algorithm) {
	Ok(c) => c,
	// Handle `islamic` calendar idenitifier.
	//
	// This should be updated depending on `icu_calendar` support and
	// intl-era-monthcode.
	Err(()) if algorithm == CalendarAlgorithm::Hijri(None) => {
	AnyCalendarKind::HijriTabularTypeIIFriday
	}
	Err(()) => return Err(TemporalError::range().with_message("unknown calendar")),
	};
	Ok(calendar_kind)

temporal/src/builtins/core/calendar.rs

Lines 106 to 108 in d125b62

	AnyCalendarKind::HijriSimulatedMecca => {
	const { &AnyCalendar::HijriSimulated(HijriSimulated::new_mecca()) }
	}