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.
{
    CPubKey vchPubKey;
    if (!pwallet->GetPubKey(keyID, vchPubKey)) {
        return;
    }
    KeyOriginInfo info;
    if (!pwallet->GetKeyOrigin(keyID, info)) {
        throw JSONRPCError(RPC_INTERNAL_ERROR, "Internal keypath is broken");
    }
    hd_keypaths.emplace(vchPubKey, std::move(info));
}
bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const CTransaction* txConst, int sighash_type, bool sign, bool bip32derivs)
{
    LOCK(pwallet->cs_wallet);
    
    bool complete = true;
    for (unsigned int i = 0; i < txConst->vin.size(); ++i) {
        const CTxIn& txin = txConst->vin[i];
        PSBTInput& input = psbtx.inputs.at(i);