feat: Rename StartTS option methods

[cynicaljoy]

BT-5313

Description

Rename the option methods that set StartTs for Event Streams and Feeds

Motivation and context

Allow a more native UX with time.Time

How was the change tested?

Updated integ tests

Screenshots (if appropriate):

Change types

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

Checklist:

• • [x] 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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