mfu_debug_level usage

Generally, most tools set mfu_debug_level = MFU_LOG_VERBOSE by default, and have a -q option which sets mfu_debug_level = MFU_LOG_NONE.

But there are several levels defined:
https://github.com/hpc/mpifileutils/blob/05055d2ad2f99291af96cd863ae59dec3d328657/src/common/mfu_util.h#L63-L71

Some tools have a hidden -d option which allows setting a specific level.

1. It would be useful to be able to pass -q, but still see errors, since MFU_LOG_NONE logs NOTHING.
2. Maybe we could more generically name mfu_debug_level to mfu_log_level
   • Or something different, since the enum is named mfu_loglevel
3. Maybe passing -q could just bump the log level down by one, instead of all the way to MFU_LOG_NONE. Then, it could be possible to pass something like -qqq to increasingly decrease the log level.
4. Along with this, maybe we can change tools from using a default of MFU_LOG_VERBOSE to using a default of MFU_LOG_INFO, since most do have a -v option which at this point doesn't really do anything. Also, most messages printed are MFU_LOG_INFO messages.
5. To incorporate all of this, we might want to evaluate some of the existing MFU_LOG_INFO messages and possibly change them to MFU_LOG_VERBOSE

Start with src/common/mfu_util.h at the mfu_loglevel definitions referenced in the issue, then inspect how the tools handle -q, -d, and -v. The issue contains several possible designs rather than one defined change, so done requires agreeing on logging-level semantics, naming, defaults, and which messages change before implementation.