Update interface with new methods and remove duplicated docs

[dpi]

Description

• interface updates: new methods, adds a variety of methods to the interface that have been added since the interface was introduced.
• Removed documentation from Pusher class. Documentation is implied when inherited from interface.

For the most part, this PR is just a bunch of move/copy-paste.

CHANGELOG

• [CHANGED] Added newly introduced methods to Pusher interface.

[dpi]

Perhaps, do the maintainers of this project consider the missing methods from the interface intentional?

Should implementors of the interface be required to add these methods?

Other ideas:

• Wait for a new major
• Add new methods to interface as @method instead, at least in the interim.
• I think the doc removals from Pusher class could happen immediately.

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