sslutil: avoid deprecation warnings from python 3.10's ssl module Use ssl.PROTOCOL_TLS_{CLIENT,SERVER} and SSLContext.{min,max}imum_version when supported (3.7+). And, catch deprecation warnings when the user asks for deprecated TLS versions (1.0 and 1.1). Differential Revision: https://phab.mercurial-scm.org/D12488