onnxruntime

Refactor session state finalization and kernel lookup usage  (#4763)

* Refactor SessionState to support coming de/serialization changes
  - move more parts into SessionState to simplify usage
  - do the kernel lookup once instead of multiple times from different places
  - rename finalize_session_state.* to session_state_utils.* as the finalization logic is now inside SessionState

* Fix some build issues

* Move subgraph session state creation into SessionState. It's not needed by GraphPartitioner any more so we can delay the creation until later. Fixes issue where EP may have removed the subgraph during partitioning when taking a control flow node, and SessionState thought the subgraph was still valid.

* Address PR comments

* Clarify a comment