[lldb][test] Move std::initializer_list from libcxx to generic directory

This just moves the test from `libcxx` to `generic`. There are currently no `std::initializer_list` formatters for libstdc++ so I didn't add a test-case for it.

Split out from llvm#146740

Author: Michael137

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/initializerlist/Makefile renamed to lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/initializer_list/Makefile

@@ -1,6 +1,3 @@
 CXX_SOURCES := main.cpp
-CXXFLAGS_EXTRAS := -std=c++11
-
-USE_LIBCPP := 1
 
 include Makefile.rules

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/initializerlist/TestInitializerList.py renamed to lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/initializer_list/TestDataFormatterStdInitializerList.py

@@ -2,7 +2,6 @@
 Test lldb data formatter subsystem.
 """
 
-
 import re
 import lldb
 from lldbsuite.test.decorators import *
@@ -11,10 +10,7 @@
 
 
 class InitializerListTestCase(TestBase):
-    @add_test_categories(["libc++"])
-    def test(self):
-        """Test that that file and class static variables display correctly."""
-        self.build()
+    def do_test(self):
         self.runCmd("file " + self.getBuildArtifact("a.out"), CURRENT_EXECUTABLE_SET)
 
         bkpt = self.target().FindBreakpointByID(
@@ -25,8 +21,6 @@ def test(self):
 
         self.runCmd("run", RUN_SUCCEEDED)
 
-        lldbutil.skip_if_library_missing(self, self.target(), re.compile(r"libc\+\+"))
-
         # The stop reason of the thread should be breakpoint.
         self.expect(
             "thread list",
@@ -39,3 +33,8 @@ def test(self):
             "frame variable ils",
             substrs=['[4] = "surprise it is a long string!! yay!!"'],
         )
+
+    @add_test_categories(["libc++"])
+    def test_libcxx(self):
+        self.build(dictionary={"USE_LIBCPP": 1})
+        self.do_test()