Move DEFAULT_MAX_RAW_TX_FEE_RATE to node/transaction.h

Summary:
So it can be used in the GUI.

Backport of Core PR17509 part [3/6] : https://github.com/bitcoin/bitcoin/pull/17509/commits/1d05a9d80b1211b47af465ba6958b0ec5a8c33ab

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D8068