JPEG/R: minor update for decoder.

Expose metadata for the decoder
Updata document
Rename "jpegr_metadata" to "jpegr_metadata_struct"

Bug: b/264715926
Test: jpegr_test

Change-Id: I6d97209453b2338996f5dc2aabfbdbe3e8a8c20c
diff --git a/libs/jpegrecoverymap/tests/jpegr_test.cpp b/libs/jpegrecoverymap/tests/jpegr_test.cpp
index 0a7d20a..be4b972 100644
--- a/libs/jpegrecoverymap/tests/jpegr_test.cpp
+++ b/libs/jpegrecoverymap/tests/jpegr_test.cpp
@@ -174,7 +174,7 @@
 }
 
 TEST_F(JpegRTest, writeXmpThenRead) {
-  jpegr_metadata metadata_expected;
+  jpegr_metadata_struct metadata_expected;
   metadata_expected.maxContentBoost = 1.25;
   metadata_expected.minContentBoost = 0.75;
   const std::string nameSpace = "http://ns.adobe.com/xap/1.0/\0";
@@ -189,7 +189,7 @@
   xmpData.insert(xmpData.end(), reinterpret_cast<const uint8_t*>(xmp.c_str()),
                   reinterpret_cast<const uint8_t*>(xmp.c_str()) + xmp.size());
 
-  jpegr_metadata metadata_read;
+  jpegr_metadata_struct metadata_read;
   EXPECT_TRUE(getMetadataFromXMP(xmpData.data(), xmpData.size(), &metadata_read));
   ASSERT_EQ(metadata_expected.maxContentBoost, metadata_read.maxContentBoost);
   ASSERT_EQ(metadata_expected.minContentBoost, metadata_read.minContentBoost);
@@ -476,7 +476,7 @@
 
   JpegRBenchmark benchmark;
 
-  jpegr_metadata metadata = { .version = 1,
+  jpegr_metadata_struct metadata = { .version = 1,
                               .maxContentBoost = 8.0f,
                               .minContentBoost = 1.0f / 8.0f };