plugins/ctf/common/metadata: logging: standardize in parser and lexer

YYDEBUG is set if the VERBOSE mode is enabled for the common metadata
module. YYFPRINTF is defined to BT_LOGV so that everything uses the
standard logging macros.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>