[WASM] JsInterop - Handle data string encoding error on negative bytes, and correct issue with js prototype global naming.

To do this, introduce a new overload `StringUtils.escapeAsUtf8(byte)` which always masks the byte to between 0 and 255 after promoting the byte to an int.  The call in BazelJ2wasmBundler already passes a byte which was previously being converted to an int between -128 to 127.

PiperOrigin-RevId: 863278945

Author: Googler

transpiler/java/com/google/j2cl/common/StringUtils.java

@@ -112,6 +112,10 @@ public static String escapeAsUtf8(String string) {
     return escaped.toString();
   }
 
+  public static String escapeAsUtf8(byte b) {
+    return escape(b & 0xFF, /* forUtf8= */ true);
+  }
+
   public static String escapeAsUtf8(int c) {
     return escape(c, /* forUtf8= */ true);
   }

transpiler/java/com/google/j2cl/transpiler/backend/wasm/WasmGenerationEnvironment.java

@@ -548,7 +548,7 @@ public static boolean isJsExport(TypeDeclaration typeDeclaration) {
 
   /** Returns the name of the global that stores the JS prototype for JsTypes. */
   public String getJsPrototypeGlobalName(TypeDeclaration typeDeclaration) {
-    return getJsPrototypeGlobalName(typeDeclaration.getQualifiedSourceName());
+    return getJsPrototypeGlobalName(typeDeclaration.getQualifiedJsName());
   }
 
   /** Returns the name of the global that stores the JS prototype for JsTypes. */