[BT-5271-streams-api] Align the Streams API with Event Feeds terminology.

[findgriffin]

Description

1. User-facing Stream API now takes an EventSource, and StreamOptions instead of StreamRequest.
2. Replace usages of toStream() with eventSource().
3. Add a new constructor to PageIterator that makes it possible to initialize with an existing page.
4. Ensure the statsCollector gets updated for feed page responses, (Leftover from PR [BT-5270-events] #162)

Still TODO are README updates, final checks of test coverage, bug bash? etc.

Motivation and context

It's worth aligning the user-facing APIs before we GA the driver.

How was the change tested?

The unit and integ tests are fairly comprehensive, I also discovered a few things while building a sample app (how to do deletes, and the PageIterator gap).

Screenshots (if appropriate):

Change types

• • Bug fix (non-breaking change that fixes an issue)
• • New feature (non-breaking change that adds functionality)
• • Breaking change (backwards-incompatible fix or feature)

Checklist:

• • My code follows the code style of this project.
• • My change requires a change to Fauna documentation.
• • My change requires a change to the README, and I have updated it accordingly.

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[pnwpedro]

Looks good in general, but one question related to stats collection.