libtracefs sql: Rename TIMESTAMP_USECS_DELTA to TIMESTAMP_DELTA_USECS

The few times I used the TIMESTAMP_USECS_DELTA I kept writing it as
TIMESTAMP_DELTA_USECS. It makes more sense to add the USECS afterward, and
it's just converting the TIMESTAMP_DELTA to use USECS.

That is, we have:

 TIMESTAMP and TIMESTAMP_USECS

We should then have

 TIMSTAMP_DELTA and TIMESTAMP_DELTA_USECS

which is just converting the TIMESTAMP_DELTA into microseconds from
nanoseconds like TIMESTAMP_USECS converts TIMESTAMP into microseconds from
nanoseconds.

Link: https://lore.kernel.org/linux-trace-devel/20240108215504.27208750@gandalf.local.home

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>