Fix #279 - Fail to render when non-VST fx are in fx chains

[firthm01]

Problem is outlined in detail in #279

The fix chosen was to replace some of our custom functions with the built-in Reaper API function for getting original plugin names in cases where plugins may have been renamed in the DAW.
This API function is only supported in REAPER v6.37+ and so the minimum version for the EPS would jump from v6.11 to v6.37. However, v6.37 is now 3 years old and anyone with a license for v6.11 should also be able to upgrade to any v6.xx version so I don't see this causing issues for many (if any) users.

Closes #279

[rsjbailey]

Just on 'stackwatch' because of the previous issue - do we call this from anywhere that will be troubled by pushing 1k onto the stack? If so:

const std::size_t fxNameMaxLen = 1023;
// I think the '\0' is superfluous, but it shouldn't hurt.
std::vector<char> fxName(fxNameMaxLen + 1, '\0'); 

if(auto fxNameRes = TrackFX_GetNamedConfigParm(track, fxNum, "fx_name", fxName.data(), fxNameMaxLen)) {
     fxName[fxNameMaxLen] = '\0'; // just in case REAPER is naughty
     name = std::string(fxName.data());
   } else {
     return false;
}

Or if we're doing it a few times

template<typename F>
std::optional<std::string> stringFromAPICall(F&& f, std::size_t maxLength = 1023) 
{
    std::vector<char> buffer(maxLength + 1, '\0');
    if(auto result = f(buffer.data(), maxLength)) {
        buffer[maxLength] = '\0'; 
        return std::string(buffer.data());
    } else { 
        return {}; 
    } 
}

and then

if(auto name = stringFromAPICall([track, fxNum](char* buffer, std::size_t size) {
  return TrackFX_GetNamedConfigParm(track, fxNum, "fx_name", buffer, size);
}) {
    // do something with *name
}

[firthm01]

I think we're safe as the old code used to allocate 64k on the stack for the entire state chunk before parsing it. That said, if you think we should go with the vector for safety anyway, happy to go ahead.

[rsjbailey]

Hah, good point. No worries then.