Merge bitcoin/bitcoin#30302: doc: clarify loadwallet path loading for wallets

ca6aa0b doc: loadwallet loads from relative walletdir (am-sq)

Pull request description:

  ## Why this change?

  bitcoin/bitcoin#30269 describes a need for documentation improvement with the `loadwallet` RPC. Namely, [some users have found](https://bitcoin.stackexchange.com/questions/123331/how-do-you-load-a-regtest-wallet) the usage description confusing when it comes to loading wallets that are not in the normal case of being in the default wallet directory.

  The default wallet directory, depending on the machine OS, has the base directory defined here: https://github.com/bitcoin/bitcoin/blob/9c5cdf07f30f816cd134e2cd2dca9c27ef7067a5/src/common/args.cpp#L699 which is then appended with `/wallets`. So for example, for MacOS, it would be `~/Library/Application Support/Bitcoin/wallets`.

  ## The changes implemented
  1. Change the help text to indicate that the filename (or directory) passed in to `loadwallet` is relative to the base wallet directory
  2. Adds additional examples to the help page showing how to fetch a wallet within a subdirectory of the base data directory for wallets, or from an absolute path

ACKs for top commit:
  achow101:
    ACK ca6aa0b
  maflcko:
    lgtm ACK ca6aa0b
  rkrux:
    ACK ca6aa0b
  jonatack:
    ACK ca6aa0b

Tree-SHA512: 123ae118c79ee1843ed65861e7a008658a53e47d4d14f2b7612561bba1b1dbdb6744f9aaac1587aac231c62d0c1804de848a6d732f1382788b437d9fe6474012

Author: achow101

src/wallet/rpc/wallet.cpp

@@ -220,7 +220,7 @@ static RPCHelpMan loadwallet()
                 "\nNote that all wallet command-line options used when starting bitcoind will be"
                 "\napplied to the new wallet.\n",
                 {
-                    {"filename", RPCArg::Type::STR, RPCArg::Optional::NO, "The wallet directory or .dat file."},
+                    {"filename", RPCArg::Type::STR, RPCArg::Optional::NO, "The path to the directory of the wallet to be loaded, either absolute or relative to the \"wallets\" directory. The \"wallets\" directory is set by the -walletdir option and defaults to the \"wallets\" folder within the data directory."},
                     {"load_on_startup", RPCArg::Type::BOOL, RPCArg::Optional::OMITTED, "Save wallet name to persistent settings and load on startup. True to add wallet to startup list, false to remove, null to leave unchanged."},
                 },
                 RPCResult{
@@ -234,8 +234,15 @@ static RPCHelpMan loadwallet()
                     }
                 },
                 RPCExamples{
-                    HelpExampleCli("loadwallet", "\"test.dat\"")
-            + HelpExampleRpc("loadwallet", "\"test.dat\"")
+                    "\nLoad wallet from the wallet dir:\n"
+                    + HelpExampleCli("loadwallet", "\"walletname\"")
+                    + HelpExampleRpc("loadwallet", "\"walletname\"")
+                    + "\nLoad wallet using absolute path (Unix):\n"
+                    + HelpExampleCli("loadwallet", "\"/path/to/walletname/\"")
+                    + HelpExampleRpc("loadwallet", "\"/path/to/walletname/\"")
+                    + "\nLoad wallet using absolute path (Windows):\n"
+                    + HelpExampleCli("loadwallet", "\"DriveLetter:\\path\\to\\walletname\\\"")
+                    + HelpExampleRpc("loadwallet", "\"DriveLetter:\\path\\to\\walletname\\\"")
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {