Locale parsing with unmatched dash locale overrides global

[joshualyon]

When making an instance call to set a locale, if the locale is supplied including the country code, but dayjs only has the generic language code, the global instance locale ends up getting overwritten.

For example, dayjs has the locale nb but if the full language tag with the country code is supplied to an instance locale() update such as nb-no, the global instance locale will get changed.

[
   dayjs.locale(),          //en
   dayjs().locale('nb-no'), //nb
   dayjs.locale()           //nb  !!global locale is changed!!
]

I suspect it's related to this fallback scenario in parseLocale() where the supplied locale is split and just the first part is recursively passed into parseLocale(), but it does not pass forward the additional parameters, so isLocal is not passed forward which ultimately causes the recursive locale parsing to improperly set the global instance locale.

dayjs/src/index.js

Lines 26 to 29 in bdcc336

	const presetSplit = preset.split('-')
	if (!l && presetSplit.length > 1) {
	return parseLocale(presetSplit[0])
	}