Merge bitcoin/bitcoin#26076: Switch hardened derivation marker to h

fe49f06c0e doc: clarify PR 26076 release note (Sjors Provoost)
bd13dc2f46 Switch hardened derivation marker to h in descriptors (Sjors Provoost)

Pull request description:

  This makes it easier to handle descriptor strings manually, especially when importing from another Bitcoin Core wallet.

  For example the `importdescriptors` RPC call is easiest to use `h` as the marker: `'["desc": ".../0h/..."]'`, avoiding the need for escape characters. With this change `listdescriptors` will use `h`, so you can copy-paste the result, without having to add escape characters or switch `'` to 'h' manually.

  Both markers can still be parsed.

  The `hdkeypath` field in `getaddressinfo` is also impacted by this change, except for legacy wallets. The latter is to prevent accidentally breaking ancient software that uses our legacy wallet.

  See discussion in #15740

ACKs for top commit:
  achow101:
    ACK fe49f06c0e
  darosior:
    re-ACK fe49f06c0e

Tree-SHA512: f78bc873b24a6f7a2bf38f5dd58f2b723e35e6b10e4d65c36ec300e2d362d475eeca6e5afa04b3037ab4bee0bf8ebc93ea5fc18102a2111d3d88fc873c08dc89

test/functional/wallet_backwards_compatibility.py

@@ -253,7 +253,7 @@ class BackwardsCompatibilityTest(BitcoinTestFramework):
         wallet = node_v17.get_wallet_rpc("u1_v17")
         address = wallet.getnewaddress("bech32")
         v17_info = wallet.getaddressinfo(address)
-        hdkeypath = v17_info["hdkeypath"]
+        hdkeypath = v17_info["hdkeypath"].replace("'", "h")
         pubkey = v17_info["pubkey"]
 
         if self.is_bdb_compiled():