Make StringPiece to be std::string_view alias

Bug: 237583012
Test: build + boot + UTs

Change-Id: I849831f4466d3b9c7ec842b75256e7fcba77a0c0
diff --git a/tools/aapt2/cmd/Optimize.cpp b/tools/aapt2/cmd/Optimize.cpp
index 042926c..9c1a2f6 100644
--- a/tools/aapt2/cmd/Optimize.cpp
+++ b/tools/aapt2/cmd/Optimize.cpp
@@ -370,8 +370,8 @@
 
     if (!kept_artifacts_.empty()) {
       for (const std::string& artifact_str : kept_artifacts_) {
-        for (const StringPiece& artifact : util::Tokenize(artifact_str, ',')) {
-          options_.kept_artifacts.insert(artifact.to_string());
+        for (StringPiece artifact : util::Tokenize(artifact_str, ',')) {
+          options_.kept_artifacts.emplace(artifact);
         }
       }
     }
@@ -403,7 +403,7 @@
 
   if (target_densities_) {
     // Parse the target screen densities.
-    for (const StringPiece& config_str : util::Tokenize(target_densities_.value(), ',')) {
+    for (StringPiece config_str : util::Tokenize(target_densities_.value(), ',')) {
       std::optional<uint16_t> target_density = ParseTargetDensityParameter(config_str, diag);
       if (!target_density) {
         return 1;