Specifically, it adds an address into the wallet.

Easy to test now thanks to https://github.com/bitcoin/bitcoin/pull/14410
```
diff --git a/test/functional/wallet_importmulti.py b/test/functional/wallet_importmulti.py
index 9ba6860..bff37b2 100755
--- a/test/functional/wallet_importmulti.py
+++ b/test/functional/wallet_importmulti.py
@@ -95,6 +95,7 @@ class ImportMultiTest(BitcoinTestFramework):
         assert_equal(address_assert['iswatchonly'], True)
         assert_equal(address_assert['ismine'], False)
         assert_equal(address_assert['timestamp'], timestamp)
+        assert_equal(address_assert['ischange'], True)
 
         # ScriptPubKey + internal + label
         self.log.info("Should not allow a label to be specified when internal is true")
```

}
    if (fRescan)
    {
        RescanWallet(*pwallet, reserver);
        pwallet->ReacceptWalletTransactions();
    }
    return NullUniValue;
}
UniValue importprunedfunds(const JSONRPCRequest& request)
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() != 2)
        throw std::runtime_error(
            "importprunedfunds\n"
            "\nImports funds without rescan. Corresponding address or script must previously be included in wallet. Aimed towards pruned wallets. The end-user is responsible to import additional transactions that subsequently spend the imported outputs or rescan after the point in the blockchain the transaction is included.\n"
            "\nArguments:\n"
            "1. \"rawtransaction\" (string, required) A raw transaction in hex funding an already-existing address in wallet\n"
            "2. \"txoutproof\"     (string, required) The hex output from gettxoutproof that contains the transaction\n"
        );
    CMutableTransaction tx;
    if (!DecodeHexTx(tx, request.params[0].get_str()))
        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
    uint256 hashTx = tx.GetHash();
    CWalletTx wtx(pwallet, MakeTransactionRef(std::move(tx)));
    CDataStream ssMB(ParseHexV(request.params[1], "proof"), SER_NETWORK, PROTOCOL_VERSION);
    CMerkleBlock merkleBlock;