net-sim: bundle the MCC/MNC list and hide MVNOs from the picker (v2.7.7)

The operator picker depended on a workspace file outside the repo
(<workspace>/samples/mcc-mnc-list.json), so a fresh clone showed
'Operator list not loaded'.

- bundle the list in the package (pysim_simple_server/data/
  mcc-mnc-list.json, byte-identical to pbakondy/mcc-mnc-list master
  commit 97bc1652, MIT) with license + provenance in
  mcc-mnc-list.LICENSE; declared as package data so wheels carry it
- _default_mcc_mnc_list() now points at the bundled file;
  --mcc-mnc-list still overrides it
- hide MVNO entries from the simulator picker (search + random): they
  do not operate their own network.  Detected via the `bands` field
  ('MVNO', 'Satellite MVNO', ...); the full list stays loaded so the
  Network state panel still resolves operator names
- tests/test_mcc_mnc.py: bundled file ships/parses, marker variants,
  search/random filters on fixtures and on the real list
- README/AGENTS updated; version trio 2.7.7; sw cache simple-v210

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simple-v209';
+const CACHE = 'simple-v210';
 const URLS = [
   'index.html',
   'help.html',