A few minor ECH -09 fixes for interop testing and fuzzing:
- selfserv now takes a PKCS8 keypair for ECH. This is more maintainable and significantly
  less terrible than parsing the ECHConfigs and cobbling one together within selfserv
  (e.g. we can support other KEMs without modifying the server).
- Get rid of the newline character in tstclnt retry_configs output.
- Fuzzer fixes in tls13_HandleHrrCookie:
 - We shouldn't use internal_error when PK11_HPKE_ImportContext fails. Cookies are
   unprotected in fuzzer mode, so this can be expected to occur.
 - Only restore the application token when recovering hash state, otherwise the
   copy could happen twice, leaking one of the allocations.

Differential Revision: https://phabricator.services.mozilla.com/D103247

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extra : moz-landing-system : lando