[Chronik] Add plugin field to TxInput in tx.py

Summary:
Allows plugins to access the plugin data of the spent inputs from previously ran plugins.

We can get this data cheaply and it makes plugins vastly more powerful as information can flow from transaction to transaction.

Depends on D16523 and D16530.

Test Plan: cargo test -p chronik-plugin-impl

Reviewers: Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D16525