test: add dlopen note checker

This introduces a test utility to validate the presence and correctness
of dlopen ELF notes.

The test extracts and compares dlopen ELF notes between the dynamic and
static versions of target binaries to catch missing entries. Furthermore,
it scans the code for dlopen_foo() invocations to ensure that no stale or
unused notes remain in the final binary, thereby verifying the linker's
garbage-collection integration.

meson.build

@@ -15,7 +15,7 @@ project('systemd', 'c',
 
 add_test_setup(
         'default',
-        exclude_suites : ['clang-tidy', 'coccinelle', 'unused-symbols', 'integration-tests'],
+        exclude_suites : ['clang-tidy', 'coccinelle', 'dlopen', 'unused-symbols', 'integration-tests'],
         exe_wrapper : find_program('tools/test-crash-trace.sh'),
         is_default : true,
 )