Intl: Remove hacks to get the supported locales of a service

[jedel1043]

We currently have some hacks to be able to get the supported locales of certain services:

boa/core/engine/src/builtins/intl/locale/utils.rs

Lines 202 to 211 in 8d857ab

	// TODO: ugly hack to accept locales that fallback to "und" in the collator/segmenter services
	Some(loc)
	if loc == candidate
	|| (loc.is_empty()
	&& [
	CollationMetadataV1Marker::KEY.path(),
	WordBreakDataV1Marker::KEY.path(),
	]
	.contains(&M::KEY.path())) =>
	{

We should remove that when the proper APIs to fetch that information are available.

[jedel1043]

Blocked on unicode-org/icu4x/issues/58