Handle Opcode::GetEffectName

[crsaracco]

Issue

Bitwig wasn't getting the VST's name anymore:

I assume this is because Bitwig used to issue a GetProductName opcode to get this, but now it's issuing the GetEffectName opcode instead.

Fix

I simply copy-pasted what we had for GetProductName and made it the GetEffectName handler too:

I know that Carla/JUCE uses this same opcode to fill in the plugin name (they call their equivalent opcode plugInOpcodeGetPlugInName here).

Question

I couldn't find out what GetProductName is supposed to be used for, from a quick glance at the Carla code. What should we do there instead?