Merge bitcoin/bitcoin#22100: refactor: Clean up new wallet spend, receive files added #21207

b11a195ef4 refactor: Detach wallet transaction methods (followup for move-only) (Russell Yanofsky)

Pull request description:

  This makes `CWallet` and `CWalletTx` methods in `spend.cpp` and `receive.cpp` files into standalone functions.

  It's a followup to [#21207 MOVEONLY: CWallet transaction code out of wallet.cpp/.h](https://github.com/bitcoin/bitcoin/pull/21207), which moved code from `wallet.cpp` to new `spend.cpp` and `receive.cpp` files.

  There are no changes in behavior. This is just making methods into functions and removing circular dependencies created by #21207. There are no comment or documentation changes, either. Removed comments from `transaction.h` are just migrated to `spend.h`, `receive.h`, and `wallet.h`.

  ---

  This commit was split off from #21206 so there are a few earlier review comments there

ACKs for top commit:
  achow101:
    ACK b11a195ef4
  Sjors:
    utACK b11a195ef4
  meshcollider:
    light ACK b11a195ef4

Tree-SHA512: 75ce818d3f03b728b14b12e2d21bd20b7be73978601989cb37ff98254393300d1bb7823281449cd3d9e40756d67d42bd9a46bbdafd2e8baa95aaf2cb1c84549f

test/functional/wallet_basic.py

@@ -600,7 +600,7 @@ class WalletTest(BitcoinTestFramework):
         total_txs = len(self.nodes[0].listtransactions("*", 99999))
 
         # Try with walletrejectlongchains
-        # Double chain limit but require combining inputs, so we pass SelectCoinsMinConf
+        # Double chain limit but require combining inputs, so we pass AttemptSelection
         self.stop_node(0)
         extra_args = ["-walletrejectlongchains", "-limitancestorcount=" + str(2 * chainlimit)]
         self.start_node(0, extra_args=extra_args)