fixes#786
stateless streamable http endpoint never closed its per request session,
so the session registry and notification subscriptions grew forever. now
the session is closed in a finally block after each request, which
triggers the existing cleanup. also removed the per request
server.onClose logging callback that accumulated on shared servers.
added tests proving sessions are removed after normal and rejected
requests. jvmTest, ktlint, detekt, apiCheck all pass. no public api
changes.
Co-authored-by: Pavel Gorgulov <devcrocod@gmail.com>
dbd34ff327