(str) java.lang.Character should have a toString(int) method

Summary

Provide toString() method that takes an int argument in parallel with the existing one that takes a char, in order to support supplementary characters seamlessly.

Problem

There's no immediate way to obtain a String from a code point.

Solution

Provide an overloaded method to Character.toString()

Specification

Add the following method:

/**
 * Returns a {@code String} object representing the
 * specified character (Unicode code point).  The result is a string of length
 * 1 or 2, consisting solely of the specified {@code codePoint}.
 *
 * @param codePoint the {@code codePoint} to be converted
 * @return the string representation of the specified {@code codePoint}
 * @exception IllegalArgumentException if the specified
 * {@code codePoint} is not a valid Unicode code point.
 * @since 11
 */
 public static String toString(int codePoint)

Append the following paragraph to the existing toString(char) method description:

   * @apiNote This method cannot handle <a
   * href="#supplementary"> supplementary characters</a>. To support
   * all Unicode characters, including supplementary characters, use
   * the {@link #toString(int)} method.