trace/perf: Rename the old collector

Rename the previous implementation of the so-called perf collector to
prepare for a replacement by a new and generic perf collector. Keep the
previous implementation for now as the new implementation won't be
compatible (in terms of API) with the old one; which should eventually
be deprecated before being removed in a future release.

Author: pietos01-arm

devlib/__init__.py

@@ -46,7 +46,7 @@
 from devlib.derived.fps import DerivedGfxInfoStats, DerivedSurfaceFlingerStats
 
 from devlib.trace.ftrace import FtraceCollector
-from devlib.trace.perf import PerfCollector
+from devlib.trace.perf_stat import PerfStatCollector
 from devlib.trace.serial_trace import SerialTraceCollector
 
 from devlib.host import LocalConnection

devlib/trace/perf_stat.py

@@ -33,7 +33,7 @@
 ]
 
 
-class PerfCollector(TraceCollector):
+class PerfStatCollector(TraceCollector):
     """
     Perf is a Linux profiling with performance counters.
 
@@ -70,7 +70,7 @@ def __init__(self, target,
                  optionstring=None,
                  labels=None,
                  force_install=False):
-        super(PerfCollector, self).__init__(target)
+        super(PerfStatCollector, self).__init__(target)
         self.events = events if events else DEFAULT_EVENTS
         self.force_install = force_install
         self.labels = labels