perf(const): const changed to a singelton

const needds to be accessed all throughout so it has been changed to a singleton to allow for more efficient usage

BREAKING CHANGE: Any previous loads to const will break, also constant->Constant and constants->Constants

tests/const/meson.build

@@ -11,7 +11,7 @@ foreach test_file : test_sources
   test_exe = executable(
       exe_name,
       test_file,
-      dependencies: gtest_dep,
+      dependencies: [gtest_dep, const_dep],
       include_directories: include_directories('../../src/const/public'),
       link_with: libconst,  # Link the dobj library
       install_rpath: '@loader_path/../../src'  # Ensure runtime library path resolves correctly