add optional define DEBUG_MUTE

[caveman99]

This shaves roughly 60k from firmware builds by not including the Logging Ressource strings. Define in variant.h or architecture.h

Stats from T-ECHO compiles:

Before:
Flash: [========  ]  81.5% (used 664700 bytes from 815104 bytes)
After:
Flash: [=======   ]  74.5% (used 606924 bytes from 815104 bytes)