Get rid of ms_isInitialized as it must be kept synchronized with
ms_loaderDll.IsLoaded() anyhow, and it's simpler to not have it at all
rather than ensuring this.
Also ensure that calling Initialize() again, after doing it first
unsuccessfully, doesn't assert because ms_loaderDll is already loaded,
by only leaving it with a valid handle if the initialization succeeded.
Closes#19041.
bc825de1fe