Rename and extend DexMerger to the wider-scope DexFileMerger.

Sufficient compatibility with
com.google.devtools.build.android.dexer.DexFileMerger
has not yet reached in this CL, see TODOs in DexFileMerger.java.

Bug: 70550158
Change-Id: Ic40d9f1e212f206af746d7e8820bdd8dfbff1dd7
diff --git a/build.gradle b/build.gradle
index 3b5e9c2..234fe25 100644
--- a/build.gradle
+++ b/build.gradle
@@ -534,11 +534,11 @@
     }
 }
 
-task DexMerger(type: Jar) {
+task DexFileMerger(type: Jar) {
     from sourceSets.main.output
-    baseName 'dexmerger'
+    baseName 'dexfilemerger'
     manifest {
-      attributes 'Main-Class': 'com.android.tools.r8.dexmerger.DexMerger'
+      attributes 'Main-Class': 'com.android.tools.r8.dexfilemerger.DexFileMerger'
     }
     // In order to build without dependencies, pass the exclude_deps property using:
     // gradle -Pexclude_deps CompatDx