Pass some rpc/blockchain RPC results and examples to RPCHelpMan
Pass some rpc/blockchain RPC results and examples to RPCHelpMan

Summary: Partial backport of Core [[https://github.com/bitcoin/bitcoin/pull/14987 | 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 patched
  ./checkrpc.sh RPCs master patched blockchain1.diff
Verify changes in `blockchain1.diff`.

Scripts:
{F4258185}
{F4258184}

blockchain1.diff:
{F4264336}

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, Fabien

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D5875

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