rpc/rawtx: Use existing NodeContext

Summary:
Also pass in appropriate object to:

• TxToJSON

This is a partial backport of core#21391
https://github.com/bitcoin/bitcoin/pull/21391/commits/7be0671b950842fc3a17641a4a21501de0a800b5

Depends on D11511

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D11512