Optimize incidentd memory usage

1. Remove dependency of libprotobuf-cpp-lite, saves .so mmap ~200KB
2. Don't use auto except iterator for readability.

Bug: 74254200
Test: adb shell dumpsys meminfo `pid incidentd`
Change-Id: If6198521c3b80929d6ea3f7ed466b5195991ccfd
diff --git a/cmds/incidentd/src/Reporter.cpp b/cmds/incidentd/src/Reporter.cpp
index 12764f8..fc8a6db 100644
--- a/cmds/incidentd/src/Reporter.cpp
+++ b/cmds/incidentd/src/Reporter.cpp
@@ -89,11 +89,11 @@
 
 IncidentMetadata::SectionStats* ReportRequestSet::sectionStats(int id) {
     if (mSectionStats.find(id) == mSectionStats.end()) {
-        auto stats = mMetadata.add_sections();
-        stats->set_id(id);
+        IncidentMetadata::SectionStats stats;
+        stats.set_id(id);
         mSectionStats[id] = stats;
     }
-    return mSectionStats[id];
+    return &mSectionStats[id];
 }
 
 // ================================================================================
@@ -182,7 +182,7 @@
             }
 
             // Execute - go get the data and write it into the file descriptors.
-            auto stats = batch.sectionStats(id);
+            IncidentMetadata::SectionStats* stats = batch.sectionStats(id);
             int64_t startTime = uptimeMillis();
             err = (*section)->Execute(&batch);
             int64_t endTime = uptimeMillis();