Introduce a `GET_MTIME` access control
This helps sharing file information via libvlc.
Libvlc applications have been requesting sorting by and accessing parsed
file statistics like mtime
since quite some time.
Implementing it as an access control will help querying this information at input item initialization and let the opportunity to the access modules to support or not this value.
Refs #18600 !2194 (merged)
Edited by Alaric Senat