Silence CryptographyDeprecationWarning (#15294)

The asyncssh library unfortunately causes log spam on
middleware startup and leaks into /var/log/syslog.

src/middlewared/middlewared/logger.py

@@ -6,6 +6,7 @@
 import warnings
 from .logging.console_formatter import ConsoleLogFormatter
 from collections import deque
+from cryptography.utils import CryptographyDeprecationWarning
 from json import dumps
 from dataclasses import dataclass
 from .utils.time_utils import utc_now
@@ -53,6 +54,9 @@
 # Excluding this default from the generated JSON schema is the correct behavior, so there is no real issue here.
 warnings.filterwarnings("ignore", module="pydantic.json_schema")
 
+# asyncssh imports various weak crypto algorithms generating log spam on every middleware start
+warnings.filterwarnings("ignore", category=CryptographyDeprecationWarning)
+
 logging.TRACE = 6
 
 APP_LIFECYCLE_LOGFILE = '/var/log/app_lifecycle.log'