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.
{
    if (state.IsValid())
        return NullUniValue;
    if (state.IsError())
        throw JSONRPCError(RPC_VERIFY_ERROR, FormatStateMessage(state));
    if (state.IsInvalid())
    {
        std::string strRejectReason = state.GetRejectReason();
        if (strRejectReason.empty())
            return "rejected";
        return strRejectReason;
    }
    
    return "valid?";
}
static std::string gbt_vb_name(const Consensus::DeploymentPos pos) {
    const struct VBDeploymentInfo& vbinfo = VersionBitsDeploymentInfo[pos];
    std::string s = vbinfo.name;
    if (!vbinfo.gbt_force) {
        s.insert(s.begin(), '!');
    }
    return s;
}
static UniValue getblocktemplate(const JSONRPCRequest& request)