Implement BlEfiGetSystemConfigurationTable() and move BlEfiGetSecureBootStatus() to desired place

xtldr/CMakeLists.txt

@@ -14,6 +14,7 @@ list(APPEND XTLDR_SOURCE
     ${XTLDR_SOURCE_DIR}/console.c
     ${XTLDR_SOURCE_DIR}/efiutil.c
     ${XTLDR_SOURCE_DIR}/string.c
+    ${XTLDR_SOURCE_DIR}/system.c
     ${XTLDR_SOURCE_DIR}/volume.c
     ${XTLDR_SOURCE_DIR}/xtldr.c)