ca6aa0b9be doc: loadwallet loads from relative walletdir (am-sq)
Pull request description:
## Why this change?
https://github.com/bitcoin/bitcoin/issues/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: 9c5cdf07f3/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 ca6aa0b9be
maflcko:
lgtm ACK ca6aa0b9be
rkrux:
ACK ca6aa0b9be
jonatack:
ACK ca6aa0b9be
Tree-SHA512: 123ae118c79ee1843ed65861e7a008658a53e47d4d14f2b7612561bba1b1dbdb6744f9aaac1587aac231c62d0c1804de848a6d732f1382788b437d9fe6474012
77bf99012a