Allow sharing of initializers between sessions. (#5092)
* Allow sharing of initializers between sessions.
* Allow sharing of initializers between sessions (2).
* Add test for C#
* Add test for C#; address PR comments
* Address PR comments
Moved AddInitializer logic to internal session options
Added tests for owned buffer
Clarified documentation
Fix bug where memory info and not device was getting compared
* Fix test
* Fix training build
* Add ver 5 end marker and ver 6 starter, add scenario and usage examples.
