cellidresolver: cache lookup results in memory

it can take literally 5s or more on moby to synthesize cell results. caching will hopefully help that.

ols/resolver/cellid/cellidresolver.py

@@ -2,6 +2,7 @@ import logging
 import os.path
 import sqlite3
 from datetime import datetime
+from functools import lru_cache
 from typing import Optional
 
 from ..base import ResolverBase
@@ -121,6 +122,7 @@ class CellIdResolver(ResolverBase):
                 now, netd['created'] * 1e6, netd['updated'] * 1e6, netd['samples']),
         }
 
+    @lru_cache
     async def resolve_cell(self, radio, opc, lac, cid, **kwargs) -> Optional[dict]:
         best_match = self._resolve_cell(radio, opc, lac, cid, self.search_network)
         if best_match is None: