ZJIT: Add tests for non-leaf classvar get and set (ruby#14924)

This commit adds tests that raise on `getclassvariable` and
`setclassvariable` to exercise the non-leaf cases as suggested in
ruby#14918 (comment)

Author: composerinteralia

test/ruby/test_zjit.rb

@@ -1675,6 +1675,20 @@ def self.test = @@x
     }
   end
 
+  def test_getclassvariable_raises
+    assert_compiles '"uninitialized class variable @@x in Foo"', %q{
+      class Foo
+        def self.test = @@x
+      end
+
+      begin
+        Foo.test
+      rescue NameError => e
+        e.message
+      end
+    }
+  end
+
   def test_setclassvariable
     assert_compiles '42', %q{
       class Foo
@@ -1686,6 +1700,21 @@ def self.test = @@x = 42
     }
   end
 
+  def test_setclassvariable_raises
+    assert_compiles '"can\'t modify frozen #<Class:Foo>: Foo"', %q{
+      class Foo
+        def self.test = @@x = 42
+        freeze
+      end
+
+      begin
+        Foo.test
+      rescue FrozenError => e
+        e.message
+      end
+    }
+  end
+
   def test_attr_reader
     assert_compiles '[4, 4]', %q{
       class C