[ISSUE #19961] first iteration of refactor stream slices

[maxi297]

What

First steps in addressing #19961 . In this PR:

• Add incremental for DatetimeBasedCursor at the retriever level
• Change stream_slicer to be an array

Notes:

• source-braze uses a custom component that is quite close to the concept of incremental and therefore, we allow custom implementation of incremental. However, the implementation is a little awkward since to implement an incremental, we need to implement StreamSlicer right now
• Some sources were defining DatetimeStreamSlicer but were not using them. See:
  • source-coin-api
  • source-punk-api
  • source-twitter
  • source-waiteraid

Concerns/questions:

• Is it ok if we still have the "stream_slice" concept exposed (like stream_slice['start_time']) as part of the incremental?
• Currently, we do not enforce that DatetimeStreamSlicer can't be inherited as a stream slicer. Is it ok?

Still TODO:

• Update the docs
• Move incremental on the stream level and rename incremental_sync
  • Add interface for incremental to always expose cursor_field
• Rename stream_slicer concept to iterable
  • Update declarative_component_schema
  • Move/rename streamslice package