feat: Gem::Requirement#initialize_copy deep-copies @requirements

to avoid accidentally mutating the original's state when doing:

```ruby
req2 = req.dup
req2.concat([">= 3.3.22"])
```

see rake-compiler/rake-compiler#236 for a
real-world use case that would be made simpler with this behavior.

lib/rubygems/requirement.rb

@@ -284,6 +284,11 @@ def _sorted_requirements
   def _tilde_requirements
     @_tilde_requirements ||= _sorted_requirements.select {|r| r.first == "~>" }
   end
+
+  def initialize_copy(other) # :nodoc:
+    @requirements = other.requirements.dup
+    super
+  end
 end
 
 class Gem::Version

test/rubygems/test_gem_requirement.rb

@@ -12,6 +12,14 @@ def test_concat
     assert_equal [[">=", v(1)], ["<", v(2)]], r.requirements
   end
 
+  def test_initialize_copy
+    r = req("= 1.2")
+    r2 = r.dup
+
+    assert_equal r.requirements, r2.requirements
+    refute_same r.requirements, r2.requirements
+  end
+
   def test_equals2
     r = req "= 1.2"
     assert_equal r, r.dup