Post-0.21: Separate wallet and node

In https://github.com/bitcoin/bitcoin/pull/16367 the various Bitcoin Core were largely separated. In the 0.21 rebase of this PR I added `libbitcoin_common_a_SOURCES` and `libbitcoin_server_a_SOURCES` to `libbitcoin_wallet_a_SOURCES` which partially undid this separation.

The reason for this was that the blocksigning RPCs, while being part of the wallet, need access to the node. Similarly the pegin RPCs also look at the current chain state and even accesses the Bitcoin RPC.

Properly separating these things may be nontrivial. Blocksigning we should likely just move to a separate utility rather than being part of the wallet. Pegin claim management will take more thought.

Comienza con PR #16367 y el 0.21 rebase, y después inspecciona libbitcoin_wallet_a_SOURCES junto con libbitcoin_common_a_SOURCES y libbitcoin_server_a_SOURCES. Rastrea las RPC de blocksigning y pegin para entender sus dependencias del nodo y del estado de la cadena. Se considera terminado cuando se restablezca la separación de wallet sin perder el comportamiento RPC requerido.

Escrito por el modelo de indexación a partir del texto del issue.