ICU-13413 Migrating some Utility class methods with Java 7 Objects class method

ICU-13413 Migrating some Utility class methods with Java 7 Objects class method

Previously, some developers accidentally introduced Java 7 Objects class utility methods. At that time, we once added Java 6 compatible implementation in com.ibm.icu.impl.Utility class. Now, we use Java 7 as the minimum supported Java version, so we can use Java 7 Objects class and methods.

There are some extra changes dropping generics type from constructor. For example from `ArrayList<String> output = new ArrayList<String>();` to `ArrayList<String> output = new ArrayList<>();`. The updated syntax is allowed since Java 7. We have eclipse project configured to normalize such expression, therefore, files touched by this commit were automatically updated. These changes are not directly related to Java 7 Objects method replacement.