[CALCITE-6135] BEARER authentication support

[Aarchy]

[stoty]

Can you open a [DISCUSS] thread on the calcite list about this change ? Explain its background in some detail ?

[Aarchy]

@stoty Based on your suggestion on the devlist, token providers now can be plugged in via config properties. Users can define their custom properties and use it in token provider's init function. There's a very basic example in the tests. On the other hand, the current way of handling properties is a bit confusing in my opinion. For now, I tried to just modify the necessary parts.