cameraservice: Migrate all internal String8/String16s to std::string

String8 and String16 are deprecated classes. It is recommended to use
std::string or std::u16string wherever possible. String16 is the native
string class for aidl, but Strings marked @utf8InCpp can use std::string
directly.

This patch standardizes libcameraservice's use of strings to
std::string, which is capable of storing utf-8 strings. This makes the
code more readable and potentially reduces the number of string copies
to a minimum.

A new set of string utils is added to frameworks/av/camera to aid this
migration.

Change-Id: I59330ac03c8a52b6c21a2388bba0c143e68af4cf
Bug: 265487852
Test: Presubmit, ran CtsCameraTestCases on Cuttlefish, adb shell dumpsys media camera and observed output
diff --git a/services/camera/libcameraservice/api2/JpegRCompositeStream.h b/services/camera/libcameraservice/api2/JpegRCompositeStream.h
index 3dfed30..016d57c 100644
--- a/services/camera/libcameraservice/api2/JpegRCompositeStream.h
+++ b/services/camera/libcameraservice/api2/JpegRCompositeStream.h
@@ -47,7 +47,7 @@
     // CompositeStream overrides
     status_t createInternalStreams(const std::vector<sp<Surface>>& consumers,
             bool hasDeferredConsumer, uint32_t width, uint32_t height, int format,
-            camera_stream_rotation_t rotation, int *id, const String8& physicalCameraId,
+            camera_stream_rotation_t rotation, int *id, const std::string& physicalCameraId,
             const std::unordered_set<int32_t> &sensorPixelModesUsed,
             std::vector<int> *surfaceIds,
             int streamSetId, bool isShared, int32_t colorSpace,