Title: Improve documentation of the filename parameter in loadwallet RPC
This PR addresses issue #30269 . The documentation for the loadwallet RPC has been improved to clarify that the filename parameter should be provided as a relative path from the wallet directory (~/.bitcoin/regtest/wallets). Additionally, two examples were added to demonstrate how to load a wallet from a different directory.
These changes aim to make the usage of the filename parameter more intuitive and prevent potential confusion for users. Please review the modifications and let me know if any further adjustments are needed. Thanks!