* Fix moderated session presence checking
Addresses all of the issues that were preventing presence checking during
moderated sessions from working as described in
[#18092](https://github.com/gravitational/teleport/issues/18092#issuecomment-1540900859).
Closes#18092
* make presence test clearer
* fix presence checking on the web ui
* Refactor web socket message handling
A single message processing loop handles retrieving the envelope
and passing it off to individual message handlers. This allows all
messages to be processed outside of `Read` which was dependent on
the terminal being active to process any messages.
The webauthn challenge response was also moved from a raw message
to a webauthn message. By sending it as a raw message it made
presence checking fail because the response has a `t` in it which
caused the session to be killed during moderated sessions.
* enforce mfa ceremony when joining and cluster wide mfa is enabled
* fix conflicts with master
* moderated tests
* Add moderated session tests for the UI
* Add moderated session integration test
* fix lints
* clean up presence test
* refactor envelope handling
* fix build
* fix: revert test debug timeout
* fix: use local context in tests
* simplify closing streams
* generalize waitForOutput to work with an io.Reader
* fix error handling in stream close
* unexport PresenceOptions
* Improve waitForOutput to match against output in successive reads
rosstimothy
553eb02bdf