MEDIUM: debug: use \x1e (RS) to delimit the condition from vaargs in DBG_COUNT()

MEDIUM: debug: use \x1e (RS) to delimit the condition from vaargs in DBG_COUNT()

The principle here is to reduce the reliance on multiple pointers in the
debug_count struct while still keeping a delimitation between records.
For this, we use the ASCII record separator character (\x1e or RS) that
is not present in the rest of our messages and has no reason to land there
by accident.

This slightly reduces the code size (2kB) but the purpose is to prepare
a next step where these definitions will benefit the BUG_ON*() macros.