Add importprivkeys RPC

The proposal mentioned is seen as advantageous and potentially simple to integrate. It suggests enhancing the current return scheme used by importdescriptors to possibly streamline or simplify implementation efforts, acknowledging this as an area where compromises might be made to avoid overextending resources. Moreover, there's an identified gap in the existing functionality of importdescriptors regarding the absence of a checksum induction flag. Introducing such a feature could diminish the reliance on the importprivkeys command, thereby improving both commands' utility and efficiency. This critique implies a perspective that sees room for significant improvements within the process of importing descriptors and private keys, which could lead to a more robust and user-friendly system.