feat: read what a Linux kernel has built and loaded, once for every driver

A kernel CVE's exploitability often hangs on code that is not there: a module
neither loaded nor shipped, an option the kernel was built without. netOrk's
KB precondition vocabulary asks exactly that (kernel_module, kernel_config).

Reading it is the same on every Linux host, so the command and its parse live
here and a driver supplies only the transport:

- KERNEL_FACTS_COMMAND: one read-only POSIX sh line, no privileges. Release,
  /proc/modules, modules.builtin, modules.dep and the build configuration
  (/boot/config-* or /proc/config.gz). The report is framed, gzipped and
  base64-encoded, so nothing in it can look like a shell prompt to a
  screen-scraping transport, and ~300 kB of configuration crosses as a fifth.
- parse_kernel_facts(): a section the command could not print comes back None,
  never empty -- "could not read" and "read, and nothing there" must stay apart.
- module_name(): no path, no .ko suffix, "-" folded to "_", as the kernel does.
- KernelFactsMixin, in the template form: get_kernel_facts() is concrete,
  _run_kernel_facts_command() is the driver's hook. Mixed in by the drivers
  that can, not by OSDriver -- a Windows host is an OS driver too, and
  hasattr(driver, "get_kernel_facts") has to stay truthful.
- KernelFactsDict in models.py. Version 2.1.0.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "napalm-device-types"
-version = "2.0.0"
+version = "2.1.0"
 description = "Abstract device-type base classes for NAPALM drivers"
 readme = "README.md"
 requires-python = ">=3.10"