Add INPUT schema checks to "apify run"

[jancurn]

If actor has an INPUT schema, then "apify run" should validate the input against the schema, using the exactly same code as Apify cloud is doing that.

[jancurn]

@mtrunkat is the schema validation code somewhere accessible?

[jancurn]

Plus it should validate that the schema is valid. But who will validate that the validator of the schema is valid, eh? :)