feat!: report the package proxy as a fact; no warnings of its own (0.9.0)

get_device_warnings decided two things for the application: that any
pending update is a warning (it re-read the updates for that), and
whether apt's proxy is the one the application's setting wants, which
it was handed as optional_args["apt_proxy_url"].

The driver reports facts instead (napalm-device-types 4.14):
get_package_proxy() says which proxy apt fetches through, None for none
or on a non-apt host; the updates are get_available_updates() as
before. get_device_warnings and the apt_proxy_url argument go.

BREAKING CHANGE: get_device_warnings and optional_args["apt_proxy_url"]
are removed. Requires napalm-device-types 4.14.

Closes #28

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "napalm-linux"
-version = "0.8.0"
+version = "0.9.0"
 description = "NAPALM driver for generic Linux systems via SSH"
 readme = "README.md"
 requires-python = ">=3.9"
@@ -37,7 +37,7 @@ classifiers = [
 ]
 dependencies = [
     "napalm>=4.0",
-    "napalm-device-types>=4.13.0",
+    "napalm-device-types>=4.14.0",
     "netmiko>=4.0.0",
     "paramiko>=5.0.0",  # CVE-2026-44405
 ]