Alias Set#=== to #include?

tests cherry picked from ruby/ruby@2aee703.
Feature https://bugs.ruby-lang.org/issues/13801.

core/src/main/java/org/jruby/ext/set/RubySet.java

@@ -466,7 +466,7 @@ public IRubyObject flatten_bang(final ThreadContext context) {
     /**
      * Returns true if the set contains the given object.
      */
-    @JRubyMethod(name = "include?", alias = { "member?" })
+    @JRubyMethod(name = "include?", alias = { "member?", "===" })
     public RubyBoolean include_p(final ThreadContext context, IRubyObject obj) {
         return context.runtime.newBoolean( containsImpl(obj) );
     }
@@ -1261,4 +1261,4 @@ final IRubyObject toRuby(Object obj) {
         return JavaUtil.convertJavaToUsableRubyObject(getRuntime(), obj);
     }
 
-}
+}

spec/ruby/core/set/case_equality_spec.rb

@@ -0,0 +1,7 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../shared/include', __FILE__)
+require 'set'
+
+describe "Set#===" do
+  it_behaves_like :set_include, :===
+end

spec/ruby/core/set/sortedset/case_equality_spec.rb

@@ -0,0 +1,7 @@
+require File.expand_path('../../../../spec_helper', __FILE__)
+require File.expand_path('../shared/include', __FILE__)
+require 'set'
+
+describe "SortedSet#===" do
+  it_behaves_like :sorted_set_include, :===
+end

test/mri/test_set.rb

@@ -200,6 +200,23 @@ def test_include?
     assert_equal(false, set.include?(true))
   end
 
+  def test_eqq
+    set = Set[1,2,3]
+
+    assert_equal(true, set === 1)
+    assert_equal(true, set === 2)
+    assert_equal(true, set === 3)
+    assert_equal(false, set === 0)
+    assert_equal(false, set === nil)
+
+    set = Set["1",nil,"2",nil,"0","1",false]
+    assert_equal(true, set === nil)
+    assert_equal(true, set === false)
+    assert_equal(true, set === "1")
+    assert_equal(false, set === 0)
+    assert_equal(false, set === true)
+  end
+
   def test_superset?
     set = Set[1,2,3]