core: extend debug allocation tracing and reduce render-time allocations

- intercept global new/delete operations in debug memory-manager builds
  - distinguish anonymous global allocations from source-tracked leaks
  - modernize eeNew to support constructor-expression syntax
  - improve memory reports with tabulated leaks and separate largest allocations
  - cache autocomplete shortcuts instead of hashing string keys on key events
  - reuse UIStyle property sets across state changes
  - reuse Text shadow colors and avoid temporary outline-color copies
  - use inline storage for temporary linear-gradient rendering data
  - make unit tests resolve assets from the executable directory
  - add memory-manager and PropertyIdSet regression coverage

src/tests/unit_tests/main.cpp

@@ -1,3 +1,11 @@
 #include "utest.h"
 
-UTEST_MAIN()
+#include <eepp/system/filesystem.hpp>
+#include <eepp/system/sys.hpp>
+
+UTEST_STATE();
+
+int main( int argc, const char* const argv[] ) {
+	EE::System::FileSystem::changeWorkingDirectory( EE::System::Sys::getProcessPath() );
+	return utest_main( argc, argv );
+}