Introduce paramIds namespace with Oscillator struct and constexpr
arrays for envelope, LFO, FX, and macro parameter IDs. Replace the
scattered local const char* arrays in Engine and PluginEditor with
references to these shared definitions.
Return ModSource::Count from modSourceFromString for unknown strings
instead of silently mapping to Lfo1. Simplify isPerVoiceSource and
isPerVoiceTarget to range-based expressions.
biggy