[mod] botdetection - improve ip_limit and link_token methods

- counting requests in LONG_WINDOW and BURST_WINDOW is not needed when the
  request is validated by the link_token method [1]

- renew a ping-key on validation [2], this is needed for infinite scrolling,
  where no new token (CSS) is loaded. / this does not fix the BURST_MAX issue in
  the vanilla limiter

- normalize the counter names of the ip_limit method to 'ip_limit.*'

- just integrate the ip_limit method straight forward in the limiter plugin /
  non intermediate code --> ip_limit now returns None or a werkzeug.Response
  object that can be passed by the plugin to the flask application / non
  intermediate code that returns a tuple

[1] https://github.com/searxng/searxng/pull/2357#issuecomment-1566113277
[2] https://github.com/searxng/searxng/pull/2357#discussion_r1208542206
[3] https://github.com/searxng/searxng/pull/2357#issuecomment-1566125979

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/botdetection/http_user_agent.py

@@ -14,11 +14,13 @@ the User-Agent_ header is unset or matches the regular expression
 """
 # pylint: disable=unused-argument
 
-from typing import Optional, Tuple
+from typing import Optional
 import re
 import flask
+import werkzeug
 
 from searx.tools import config
+from ._helpers import too_many_requests
 
 
 USER_AGENT = (
@@ -48,11 +50,8 @@ def regexp_user_agent():
     return _regexp
 
 
-def filter_request(request: flask.Request, cfg: config.Config) -> Optional[Tuple[int, str]]:
+def filter_request(request: flask.Request, cfg: config.Config) -> Optional[werkzeug.Response]:
     user_agent = request.headers.get('User-Agent', 'unknown')
     if regexp_user_agent().match(user_agent):
-        return (
-            429,
-            f"bot detected, HTTP header User-Agent: {user_agent}",
-        )
+        return too_many_requests(request, f"bot detected, HTTP header User-Agent: {user_agent}")
     return None