This change adds the ability to mount a a single folder or a volume
inside another folder, using the bind filter API.

While the API allows mounting multiple sources inside a single mount
point, acting as an overlay, we disable this functionality in the ApplyFileBinding
function.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

  * Properly close handle in getFinalPath()
  * Use string in function signature. mksyscall generates proper code to
    convert to utf16
  * Enable TestRemoveFileBinding on Windows Server 2019

Windows Server 2019 only exposes 2 function in bindfltapi.dll:

  * BfRemoveMapping
  * BfSetupFilter

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

  * Additionally check if we can write to a read-only mount point, not
    just delete from it
  * No need to set FILE_FLAG_OPEN_REPARSE_POINT when opening a file

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>