zonefs: add tracepoints for file operations

Add tracepoints for file I/O operations to aid in debugging of I/O errors
with zonefs.

The added tracepoints are in:
- zonefs_zone_mgmt() for tracing zone management operations
- zonefs_iomap_begin() for tracing regular file I/O
- zonefs_file_dio_append() for tracing zone-append operations

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>