`ctf` plugin: metadata: use local log level

`ctf` plugin: metadata: use local log level

As of this patch, the users of the common metadata functions and objects
set the new log level parameters to their own (global) log level.

The goal is to eventually have a per-component log level for the `ctf`
plugin's component classes.

Unfortunately, `YYFPRINTF` and `YY_FATAL_ERROR` are pretty limited in
terms of available context. I'm leaving the
`BABELTRACE_PLUGIN_CTF_METADATA_LOG_LEVEL` environment variable to set
the logging level of the parser and lexer modules.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Change-Id: I34651e6d0c14b5acc9b4198681c2aea4c003dc7a
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1490
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Francis Deslauriers <francis.deslauriers@efficios.com>