Remove log_function and its uses (#11761)

I've never found this terribly useful. I think it was added in the early days
of Synapse, without much thought as to what would actually be useful to log,
and has just been cargo-culted ever since.

Rather, it tends to clutter up debug logs with useless information.

synapse/logging/utils.py

@@ -1,76 +0,0 @@
-# Copyright 2014-2016 OpenMarket Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-
-import logging
-from functools import wraps
-from inspect import getcallargs
-from typing import Callable, TypeVar, cast
-
-_TIME_FUNC_ID = 0
-
-
-def _log_debug_as_f(f, msg, msg_args):
-    name = f.__module__
-    logger = logging.getLogger(name)
-
-    if logger.isEnabledFor(logging.DEBUG):
-        lineno = f.__code__.co_firstlineno
-        pathname = f.__code__.co_filename
-
-        record = logger.makeRecord(
-            name=name,
-            level=logging.DEBUG,
-            fn=pathname,
-            lno=lineno,
-            msg=msg,
-            args=msg_args,
-            exc_info=None,
-        )
-
-        logger.handle(record)
-
-
-F = TypeVar("F", bound=Callable)
-
-
-def log_function(f: F) -> F:
-    """Function decorator that logs every call to that function."""
-    func_name = f.__name__
-
-    @wraps(f)
-    def wrapped(*args, **kwargs):
-        name = f.__module__
-        logger = logging.getLogger(name)
-        level = logging.DEBUG
-
-        if logger.isEnabledFor(level):
-            bound_args = getcallargs(f, *args, **kwargs)
-
-            def format(value):
-                r = str(value)
-                if len(r) > 50:
-                    r = r[:50] + "..."
-                return r
-
-            func_args = ["%s=%s" % (k, format(v)) for k, v in bound_args.items()]
-
-            msg_args = {"func_name": func_name, "args": ", ".join(func_args)}
-
-            _log_debug_as_f(f, "Invoked '%(func_name)s' with args: %(args)s", msg_args)
-
-        return f(*args, **kwargs)
-
-    wrapped.__name__ = func_name
-    return cast(F, wrapped)