The `generate` RPC method:
- was introduced in 2010
- is now only used for testing
- reaches across multiple components (wallet, mining)

I propose we remove the wallet `generate` RPC method and update all tests to use the `generatetoaddress` RPC method. We can do this non-invasively in the test framework by adding a `generate` method to `TestNode` so that the individual tests do not need to be updated. We could also add a `generate` alias to the `generatetoaddress` RPC method.

Doing this removes a wallet->server dependency and simplifies the wallet->server interface (#10973).

I'm opening this issue before implementing in case anyone has objections.
{
    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() != 1)
        throw std::runtime_error(
            "backupwallet \"destination\"\n"
            "\nSafely copies current wallet file to destination, which can be a directory or a path with filename.\n"
            "\nArguments:\n"
            "1. \"destination\"   (string) The destination directory or file\n"
            "\nExamples:\n"
            + HelpExampleCli("backupwallet", "\"backup.dat\"")
            + HelpExampleRpc("backupwallet", "\"backup.dat\"")
        );
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    LOCK2(cs_main, pwallet->cs_wallet);
    std::string strDest = request.params[0].get_str();
    if (!pwallet->BackupWallet(strDest)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Error: Wallet backup failed!");
    }
    return NullUniValue;
}
static UniValue keypoolrefill(const JSONRPCRequest& request)