feat(richtext-lexical)!: simplify creation of features

[AlessioGr]

• Adds new createServerFeature and createClientFeature helper functions to create new features without boilerplate.
• Makes some props optional which were previously required
• The feature prop, for both server & client features, now also accept normal objects. Functions are rarely need there

BREAKING:

• ServerFeature: ClientComponent has been renamed to ClientFeature
• ServerFeature: The nested serverFeatureProps has been renamed to sanitizedServerFeatureProps
• ServerFeature: The FeatureProviderProviderServer type now expects 3 generics instead of 2. We have split the props generic into sanitized & unsanitized props
• ClientFeature: The FeatureProviderProviderClient type now expects 2 generics instead of 1. We have split the props generic into sanitized & unsanitized props
• ClientFeature: The nested clientFeatureProps has been renamed to sanitizedClientFeatureProps