chore: adopt the NAPALM driver standard

- CI moves to .gitea/workflows/ci.yml and calls the shared driver workflow
  of NAPALM/driver-standard; .github/ is gone.
- napalm-device-types >=4.21.1 from PyPI (the README no longer installs
  it from git), py.typed, SPDX license string, setuptools>=77, version
  floors on the dev extra, Issues and Changelog links on git.netork.io.
- mypy strict for the package; napalm_bsd.base, napalm_bsd.freebsd and
  napalm_bsd.openbsd are exempt for now (28 errors, mostly getters typed
  as plain dicts rather than the device-types TypedDicts), recorded in the
  quality baseline with three complex parsers. parse.py is strict after a
  one-line annotation.
- Coverage floor 94 % (measured 94.63 %).

.gitea/workflows/ci.yml

@@ -0,0 +1,15 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*"]
+  pull_request:
+
+jobs:
+  driver:
+    uses: NAPALM/driver-standard/.gitea/workflows/driver.yml@main
+    with:
+      standard-ref: main
+    secrets:
+      PYPI_TOKEN: ${{ secrets.PYPI_TOKEN }}