FEATURE: allow user to override watched_precedence_over_muted setting (#22340)

Recently, site setting watched_precedence_over_muted was introduced - https://github.com/discourse/discourse/pull/22252

In this PR, we are allowing users to override it. The option is only displayed when the user has watched categories and muted tags, or vice versa.

spec/requests/api/schemas/json/user_get_response.json

@@ -777,6 +777,9 @@
             "sidebar_show_count_of_new_items": {
               "type": "boolean"
             },
+            "watched_precedence_over_muted": {
+              "type": ["boolean", "null"]
+            },
             "seen_popups": {
               "type": ["array", "null"]
             }