Mass refactoring: Change JNI #includes to use full paths (webrtc/).

Using relative paths for JNI includes is causing build failures in chromium.

WebRTC already uses full include paths for generated JNI headers, so this CL
just removes the "jni_package" parameter from WebRTC generate_jni() targets
and removes the "jni/" portion of includes. The "jni_package" variable will be
removed from the generate_jni() template shortly.

To fix includes:
find . -name *.cc -exec sed -i -E 's@(#include.+generated.+jni)/jni/(.+_jni.h)@\1/\2@' {} \;

See https://groups.google.com/a/chromium.org/forum/?#!topic/java/MEovGrAwbqI
for discussion on naming scheme.

No-Try: True
TBR: kwiberg@webrtc.org
Bug: chromium:964169
Change-Id: I758c1b41bf6f5005587e55b82f14065fe251baad
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/143521
Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28380}

examples/androidnativeapi/BUILD.gn

@@ -31,7 +31,6 @@ if (is_android) {
     sources = [
       "java/org/webrtc/examples/androidnativeapi/CallClient.java",
     ]
-    jni_package = ""
     namespace = "webrtc_examples"
     jni_generator_include = "//sdk/android/src/jni/jni_generator_helper.h"
   }

examples/androidnativeapi/jni/android_call_client.cc

@@ -15,7 +15,7 @@
 #include "absl/memory/memory.h"
 #include "api/peer_connection_interface.h"
 #include "api/task_queue/default_task_queue_factory.h"
-#include "examples/androidnativeapi/generated_jni/jni/CallClient_jni.h"
+#include "examples/androidnativeapi/generated_jni/CallClient_jni.h"
 #include "logging/rtc_event_log/rtc_event_log_factory.h"
 #include "media/engine/internal_decoder_factory.h"
 #include "media/engine/internal_encoder_factory.h"