Pull request: 5190-clear-cache

Updates #4695.
Updates #5190.

Squashed commit of the following:

commit f4156f54ebd1b0c96318715441da1dc54cbbfb0f
Author: Ildar Kamalov <ik@adguard.com>
Date:   Fri Dec 2 16:19:03 2022 +0300

    client: button styles

commit 42cd8ac8ac1abb5c43a42065e2374d11f2d9a62b
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Dec 2 15:39:15 2022 +0300

    all: upd dnsproxy

commit 87b04391afeaed28523448aa12a317300e718b72
Author: Ildar Kamalov <ik@adguard.com>
Date:   Fri Dec 2 15:19:07 2022 +0300

    client: add clear cache button

commit ee99548b3689ce47959d9bddc6a1e866e773dcc3
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Dec 1 18:54:54 2022 +0300

    all: add cache clear

openapi/openapi.yaml

@@ -94,6 +94,15 @@
       'responses':
         '200':
           'description': 'OK'
+  '/cache_clear':
+    'post':
+      'tags':
+      - 'global'
+      'operationId': 'cacheClear'
+      'summary': 'Clear DNS cache'
+      'responses':
+        '200':
+          'description': 'OK'
   '/test_upstream_dns':
     'post':
       'tags':