introduce function registry

[samuelstroschein]

Context

Fink and paraglide started using functions like plural. The signature between both implementations needs to be identical.

Proposal

Introduce a function registry with v2 to avoid chaos.

• remove plural logic from ui components

	private _getPluralCategories = (): string[] | undefined => {
		return this.message?.locale
			? [...new Intl.PluralRules(this.message.locale).resolvedOptions().pluralCategories, "*"]
			: undefined
	}

[samuelstroschein]

moved from sdk v2 to dedicated project because