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() > 2) {
        throw std::runtime_error(
            "rescanblockchain (\"start_height\") (\"stop_height\")\n"
            "\nRescan the local blockchain for wallet related transactions.\n"
            "\nArguments:\n"
            "1. \"start_height\"    (numeric, optional) block height where the rescan should start\n"
            "2. \"stop_height\"     (numeric, optional) the last block height that should be scanned\n"
            "\nResult:\n"
            "{\n"
            "  \"start_height\"     (numeric) The block height where the rescan has started. If omitted, rescan started from the genesis block.\n"
            "  \"stop_height\"      (numeric) The height of the last rescanned block. If omitted, rescan stopped at the chain tip.\n"
            "}\n"