[Chronik] Add PluginsWrite::{insert, delete}

Summary:
This actually runs the plugins and returns the results in the protobuf.

Depends on D16527 and D16528.

Test Plan: ninja check-functional

Reviewers: Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D16532