* [stable-2.8] eos_config: Fix test issues (#56180)
* Alter tests to pass
* Change diff_against to make changed work again
* Add another diff_against
* Expose supports_sessions across all EOS connection types
* Change session warning to failure
* supports_sessions needs to be a method to survive the rpc boundary
* Alter tests to match
(cherry picked from commit 0bead36)