Update intent and slot name validation

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The new built-in intent library brings some additions to intent and slot names.

See: https://developer.amazon.com/public/solutions/alexa/alexa-skills-kit/docs/built-in-intent-ref/built-in-intent-library

For instance, this is valid intent name: AMAZON.SearchAction<object@WeatherForecast[temperature]> (one of many)
And this is valid slot name: object.location.addressLocality.name

TODO intents:

• extend the intent name validation to support all old built-in intents like AMAZON.YesIntent, ... and all others
• extend the intent name validation to support new built-in intents library (see docs) - it will be probably necessary to list all of them in some json - but hopefully there is better solution. For sure AMAZON.MyMadeUpIntent is not supported - and yields error when adding to intent schema in developer portal so some kind of mapping is probably required
• deprecate app.builtInIntent() - will be removed from 3.0.0 and show warning message on use
• document and mention also in warning that an alternative to f.e. app.builtInIntent('yes', ...) is `app.intent('AMAZON.YesIntent', ...)
• Note: it would be much easier to just remove intent name validation completely and just rely on the developer portal validation - needs discussion

TODO slots:

• enable the use of f.e.: slots.object.location.addressLocality.name when slot name is (string) object.location.addressLocality.name
• research possible forms of slot names and fix how they are accessed