logcat: test: inject() tuning

Add a hidden -v nsec flag to logcat (actually logprint in liblog.so)
so that we can do more exacting tests of logcat.tail_time.  Halve the
spam pressure of logcat.tail_* in inject() routine, and give us a few
more retries at the higher counts.  Add instrumentation to
logcat.logrotate failures.  Add inject for logcat.year test.

Test: gTest logcat-unit-tests
Bug: 34454772
Change-Id: If6f3bd21892c8a2b9ccee8c8bbf592a1ae0b2a57
diff --git a/logcat/logcat.cpp b/logcat/logcat.cpp
index d9935c3..4a171fd 100644
--- a/logcat/logcat.cpp
+++ b/logcat/logcat.cpp
@@ -298,6 +298,8 @@
                     "                  and individually flagged modifying adverbs can be added:\n"
                     "                    color descriptive epoch monotonic printable uid\n"
                     "                    usec UTC year zone\n"
+                    // private and undocumented nsec, no signal, too much noise
+                    // useful for -T or -t <timestamp> accurate testing though.
                     "  -D, --dividers  Print dividers between each log buffer\n"
                     "  -c, --clear     Clear (flush) the entire log and exit\n"
                     "                  if Log to File specified, clear fileset instead\n"