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 (request.fHelp || request.params.size() < 1 || request.params.size() > 2)
        throw std::runtime_error(
            "estimaterawfee conf_target (threshold)\n"
            "\nWARNING: This interface is unstable and may disappear or change!\n"
            "\nWARNING: This is an advanced API call that is tightly coupled to the specific\n"
            "         implementation of fee estimation. The parameters it can be called with\n"
            "         and the results it returns will change if the internal implementation changes.\n"
            "\nEstimates the approximate fee per kilobyte needed for a transaction to begin\n"
            "confirmation within conf_target blocks if possible. Uses virtual transaction size as\n"
            "defined in BIP 141 (witness data is discounted).\n"
            "\nArguments:\n"
            "1. conf_target (numeric) Confirmation target in blocks (1 - 1008)\n"
            "2. threshold   (numeric, optional) The proportion of transactions in a given feerate range that must have been\n"
            "               confirmed within conf_target in order to consider those feerates as high enough and proceed to check\n"
            "               lower buckets.  Default: 0.95\n"
            "\nResult:\n"
            "{\n"
            "  \"short\" : {            (json object, optional) estimate for short time horizon\n"
            "      \"feerate\" : x.x,        (numeric, optional) estimate fee rate in " + CURRENCY_UNIT + "/kB\n"
            "      \"decay\" : x.x,          (numeric) exponential decay (per block) for historical moving average of confirmation data\n"
            "      \"scale\" : x,            (numeric) The resolution of confirmation targets at this time horizon\n"
            "      \"pass\" : {              (json object, optional) information about the lowest range of feerates to succeed in meeting the threshold\n"