SWDEV-513197 - Unify getBuffer implementation

- Use getBuffer/releaseBuffer in BlitManager
- Cleanup XferBuffer as we use ManagedBuffer for both reads/writes

Change-Id: I2661b85dd012763b17a38a743fec1b1d79125f67


[ROCm/clr commit: 37d606d193]

projects/clr/rocclr/device/rocm/rocsettings.cpp

@@ -53,8 +53,6 @@ Settings::Settings() {
   // Disable image DMA by default (ROCM runtime doesn't support it)
   imageDMA_ = false;
 
-  stagedXferRead_ = true;
-  stagedXferWrite_ = true;
   stagedXferSize_ = flagIsDefault(GPU_STAGING_BUFFER_SIZE)
       ? 1 * Mi : GPU_STAGING_BUFFER_SIZE * Mi;