[net/refactor] Remove fFeeler flag from CNode

Summary:
Partial backport (11/19) of core PR19316:
https://github.com/bitcoin/bitcoin/pull/19316/commits/14923422b08ac4b21b35c426bf0e1b9e7c97983b

Depends on D8720.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK, majcosta

Reviewed By: #bitcoin_abc, PiRK, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8721