8141132: JEP 254: Compact Strings

Adopt a more space-efficient internal representation for strings.

Co-authored-by: Brent Christian <brent.christian@oracle.com>
Co-authored-by: Vivek Deshpande <vivek.r.deshpande@intel.com>
Co-authored-by: Charlie Hunt <charlie.hunt@oracle.com>
Co-authored-by: Vladimir Kozlov <vladimir.kozlov@oracle.com>
Co-authored-by: Roger Riggs <roger.riggs@oracle.com>
Co-authored-by: Xueming Shen <xueming.shen@oracle.com>
Co-authored-by: Aleksey Shipilev <aleksey.shipilev@oracle.com>
Co-authored-by: Sandhya Viswanathan <sandhya.viswanathan@intel.com>
Reviewed-by: alanb, bdelsart, coleenp, iklam, jiangli, jrose, kevinw, naoto, pliden, roland, smarks, twisti

jdk/src/java.base/share/classes/java/util/Arrays.java

@@ -2685,6 +2685,7 @@ public class Arrays {
      * @param a2 the other array to be tested for equality
      * @return {@code true} if the two arrays are equal
      */
+    @HotSpotIntrinsicCandidate
     public static boolean equals(byte[] a, byte[] a2) {
         if (a==a2)
             return true;