Move BlackboxMappedMetricLogger to acts.metrics.loggers, and refactor BlackboxMetricLogger as a subclass of the former.

Bug: None
Test: local acts test, unit tests
Change-Id: I1f8f19432479b668b1bcc54cf69a29b5fee8600e
diff --git a/acts/tests/google/wifi/WifiSensitivityTest.py b/acts/tests/google/wifi/WifiSensitivityTest.py
index 9d6ba59..a64fe58 100644
--- a/acts/tests/google/wifi/WifiSensitivityTest.py
+++ b/acts/tests/google/wifi/WifiSensitivityTest.py
@@ -27,6 +27,7 @@
 from acts import utils
 from acts.controllers import iperf_client
 from acts.controllers.utils_lib import ssh
+from acts.metrics.loggers.blackbox import BlackboxMappedMetricLogger
 from acts.test_utils.wifi import ota_chamber
 from acts.test_utils.wifi import wifi_performance_test_utils as wputils
 from acts.test_utils.wifi import wifi_test_utils as wutils
@@ -126,9 +127,9 @@
     def __init__(self, controllers):
         base_test.BaseTestClass.__init__(self, controllers)
         self.testcase_metric_logger = (
-            wputils.BlackboxMappedMetricLogger.for_test_case())
+            BlackboxMappedMetricLogger.for_test_case())
         self.testclass_metric_logger = (
-            wputils.BlackboxMappedMetricLogger.for_test_class())
+            BlackboxMappedMetricLogger.for_test_class())
         self.publish_testcase_metrics = True
 
     def setup_class(self):
@@ -623,9 +624,9 @@
     def __init__(self, controllers):
         base_test.BaseTestClass.__init__(self, controllers)
         self.testcase_metric_logger = (
-            wputils.BlackboxMappedMetricLogger.for_test_case())
+            BlackboxMappedMetricLogger.for_test_case())
         self.testclass_metric_logger = (
-            wputils.BlackboxMappedMetricLogger.for_test_class())
+            BlackboxMappedMetricLogger.for_test_class())
         self.publish_testcase_metrics = False
 
     def setup_class(self):