Allow net and media CTS tests to use hidden APIs

MediaRecorderTest uses EncoderCapabilities.getVideoEncoders().
WifiManagerTest uses WifiManager.getTxPackageCount().

Pass the 'hidden-api-checks=false' flag to temporarily exempt the two
CTS packages from the hidden api check. We eventually should fix the
hidden API usage completely or exempt the violating tests only.

Bug: 77436928
Test: atest CtsMediaTestCases
Test: atest CtsNetTestCases
Change-Id: I85efbb08c24b87079c0360fc3f9a2267462592f0

tests/cts/net/AndroidTest.xml

@@ -23,5 +23,6 @@
     <test class="com.android.tradefed.testtype.AndroidJUnitTest" >
         <option name="package" value="android.net.cts" />
         <option name="runtime-hint" value="9m4s" />
+        <option name="hidden-api-checks" value="false" />
     </test>
 </configuration>