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.
+ HelpExampleRpc("keypoolrefill", "")
        );
    if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Error: Private keys are disabled for this wallet");
    }
    LOCK2(cs_main, pwallet->cs_wallet);
    
    unsigned int kpSize = 0;
    if (!request.params[0].isNull()) {
        if (request.params[0].get_int() < 0)
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, expected valid size.");
        kpSize = (unsigned int)request.params[0].get_int();
    }
    EnsureWalletIsUnlocked(pwallet);
    pwallet->TopUpKeyPool(kpSize);
    if (pwallet->GetKeyPoolSize() < kpSize) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Error refreshing keypool.");
    }
    return NullUniValue;
}
static void LockWallet(CWallet* pWallet)
{
    LOCK(pWallet->cs_wallet);
    pWallet->nRelockTime = 0;
    pWallet->Lock();
}
static UniValue walletpassphrase(const JSONRPCRequest& request)
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();