Merge #12560: [wallet] Upgrade path for non-HD wallets to HD

a8da482 Bump wallet version for pre split keypool (Andrew Chow)
dfcd9f3 Use a keypool of presplit keys after upgrading to hd chain split (Andrew Chow)
5c50e93 Allow -upgradewallet to upgradewallets to HD (Andrew Chow)
2bcf2b5 Test sethdseed (Andrew Chow)
b5ba01a Add 'sethdseed' RPC to initialize or replace HD seed (Chris Moore)
dd3c07a Separate HaveKey function that checks whether a key is in a keystore (Andrew Chow)

Pull request description:

  Revival/rebase of #11085

  Adds a new command `sethdseed` which allows you to either set or generate a new HD seed to be used. A new keypool can be generated or the original one kept and new keys added to the keypool will come from the new HD seed.

  Wallets that are not HD will be upgraded to be version FEATURE_HD_SPLIT when the `sethdseed` RPC command is used.

  I have also add some tests for this.

  Additionally `-upgradewallet` can now be used to upgrade a wallet from non-HD to HD. When it is used for such an upgrade, the keypool will be regenerated.

Tree-SHA512: e56c792e150590429ac4a1061e8d6f7b20cca06366e184eb9bbade4cd6ae82699a28fe84f87031eadba97ad2c1606517a105f00fb7b45779c979243020071adb

src/rpc/client.cpp

@@ -38,6 +38,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "sendtoaddress", 5 , "replaceable" },
     { "sendtoaddress", 6 , "conf_target" },
     { "settxfee", 0, "amount" },
+    { "sethdseed", 0, "newkeypool" },
     { "getreceivedbyaddress", 1, "minconf" },
     { "getreceivedbyaccount", 1, "minconf" },
     { "getreceivedbylabel", 1, "minconf" },