Zend/tests: merge constant_expressions into constexpr, update names (#17872)

While reviewing the existing tests in the `constexpr` directory, I found that
some of the names were not updated to reflect the contents when the contents
were changed in #9301.

Follow-up to #15638

Author: DanielEScherzer

Zend/tests/constant_expressions/class_on_expression_in_constant_expression.phpt renamed to Zend/tests/constexpr/class_on_expression_in_constant_expression.phpt

@@ -1,5 +1,5 @@
 --TEST--
-Dynamic class name in new is not supported
+Dynamic class name in new is supported
 --FILE--
 <?php
 

Zend/tests/constant_expressions/constant_expressions.phpt renamed to Zend/tests/constexpr/constant_expressions.phpt

@@ -1,5 +1,5 @@
 --TEST--
-Invalid operation in new arg in const expr
+Valid operation in new arg in const expr
 --FILE--
 <?php
 

Zend/tests/constant_expressions/constant_expressions_arrays.phpt renamed to Zend/tests/constexpr/constant_expressions_arrays.phpt

@@ -1,5 +1,5 @@
 --TEST--
-Static in new is not supported
+Static in new is supported
 --FILE--
 <?php