Pass zmq RPC results and examples to RPCHelpMan

Summary: Partial backport of Core PR14987

Test Plan:
On master:

ninja
./bitcoind
./bitcoin-cli help > RPCs
./getrpchelps.sh RPCs master

Then on the patched branch:

ninja
./bitcoind
./getrpchelps.sh RPCs zmqPatched
./checkrpc.sh RPCs master zmqPatched zmq.diff

Verify zmq.diff does not exist.

Scripts:

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5818