`getblock` is slow on verbosity, it's happened because `LOCK(cs_main)` applied for whole function including JSON generation
https://github.com/bitcoin/bitcoin/blob/ef70f9b52b851c7997a9f1a0834714e3eebc1fd8/src/rpc/blockchain.cpp#L810

I added few lines which print spent time:
```cpp
    LOCK(cs_main);
    auto t1 = std::chrono::high_resolution_clock::now();
...
    auto t2 = std::chrono::high_resolution_clock::now();
    auto ret = blockToJSON(block, pblockindex, verbosity >= 2);
    auto t3 = std::chrono::high_resolution_clock::now();
    std::cout << "blockToJSON " << pblockindex->nHeight << ": " << std::chrono::duration_cast<std::chrono::microseconds>(t2 - t1).count() << " " << std::chrono::duration_cast<std::chrono::microseconds>(t3 - t1).count() << std::endl;
    return ret;
```

and numbers looks like:
```
blockToJSON 570019: 14727 201870
blockToJSON 570022: 16049 225224
blockToJSON 570021: 33776 217398
blockToJSON 570020: 21754 191669
blockToJSON 570023: 30949 236941
blockToJSON 570025: 23346 223673
blockToJSON 570024: 18732 203002
blockToJSON 570026: 17467 216213
blockToJSON 570027: 16658 217395
blockToJSON 570028: 19015 219183
```

i.e. everything before JSON generation takes 15-30ms, while JSON takes minimum 190ms and lock `cs_main` for all this time. As result it's possible extract only ~5 blocks per second.

Looking on the code I think it's possible copy data from `CBlockIndex` to extra structure, so in this case `cs_main` can be unlocked right after `GetBlockChecked`.
https://github.com/bitcoin/bitcoin/blob/ef70f9b52b851c7997a9f1a0834714e3eebc1fd8/src/rpc/blockchain.cpp#L828
As result `getblock` in verbosity mode should be much faster (in case if `-rpcthreads` will be adjusted too).

Does this make sense?
{
    if (request.fHelp || request.params.size() < 1 || request.params.size() > 2)
        throw std::runtime_error(
            RPCHelpMan{"scantxoutset",
                "\nEXPERIMENTAL warning: this call may be removed or changed in future releases.\n"
                "\nScans the unspent transaction output set for entries that match certain output descriptors.\n"
                "Examples of output descriptors are:\n"
                "    addr(<address>)                      Outputs whose scriptPubKey corresponds to the specified address (does not include P2PK)\n"
                "    raw(<hex script>)                    Outputs whose scriptPubKey equals the specified hex scripts\n"
                "    combo(<pubkey>)                      P2PK, P2PKH, P2WPKH, and P2SH-P2WPKH outputs for the given pubkey\n"
                "    pkh(<pubkey>)                        P2PKH outputs for the given pubkey\n"
                "    sh(multi(<n>,<pubkey>,<pubkey>,...)) P2SH-multisig outputs for the given threshold and pubkeys\n"
                "\nIn the above, <pubkey> either refers to a fixed public key in hexadecimal notation, or to an xpub/xprv optionally followed by one\n"
                "or more path elements separated by \"/\", and optionally ending in \"/*\" (unhardened), or \"/*'\" or \"/*h\" (hardened) to specify all\n"
                "unhardened or hardened child keys.\n"
                "In the latter case, a range needs to be specified by below if different from 1000.\n"
                "For more information on output descriptors, see the documentation in the doc/descriptors.md file.\n",
                {
                    {"action", RPCArg::Type::STR, RPCArg::Optional::NO, "The action to execute\n"
            "                                      \"start\" for starting a scan\n"
            "                                      \"abort\" for aborting the current scan (returns true when abort was successful)\n"
            "                                      \"status\" for progress report (in %) of the current scan"},
                    {"scanobjects", RPCArg::Type::ARR, RPCArg::Optional::NO, "Array of scan objects\n"
            "                                  Every scan object is either a string descriptor or an object:",
                        {
                            {"descriptor", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "An output descriptor"},
                            {"", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED, "An object with output descriptor and metadata",