docs: auto-generate Card Filesystem Reference

Add a Sphinx extension (docs/pysim_fs_sphinx.py) that hooks into the
builder-inited event and generates docs/filesystem.rst before Sphinx
reads any source files.

The generated page contains a hierarchical listing of all implemented
EFs and DFs, organised by application/specification (UICC/TS 102 221,
ADF.USIM/TS 31.102, ADF.ISIM/TS 31.103, SIM/TS 51.011).  For each file,
the class docstring and any _test_de_encode / _test_decode vectors
are included as an encoding/decoding example table.

docs/filesystem.rst is fully generated at build time and is therefore
added to .gitignore.

Add tests/unittests/test_fs_coverage.py that walks all pySim.* modules
and verifies that every CardProfile, CardApplication, and standalone
CardDF subclass with EF/DF children is either listed in the SECTIONS
(and will appear in the docs) or explicitly EXCLUDED.

Change-Id: I06ddeefc6c11e04d7c24e116f3f39c8a6635856f
Related: OS#6316

docs/conf.py

@@ -13,6 +13,7 @@
 import os
 import sys
 sys.path.insert(0, os.path.abspath('..'))
+sys.path.insert(0, os.path.abspath('.'))   # for local extensions (pysim_fs_sphinx, ...)
 
 
 # -- Project information -----------------------------------------------------
@@ -39,7 +40,8 @@ extensions = [
         "sphinx.ext.autodoc",
         "sphinxarg.ext",
         "sphinx.ext.autosectionlabel",
-        "sphinx.ext.napoleon"
+        "sphinx.ext.napoleon",
+        "pysim_fs_sphinx",
 ]
 
 # Add any paths that contain templates here, relative to this directory.
@@ -78,6 +80,7 @@ autodoc_mock_imports = ['klein', 'twisted']
 # of autosectionlabel duplicate-label warnings - suppress them.
 autosectionlabel_maxdepth = 3
 suppress_warnings = [
+    'autosectionlabel.filesystem',
     'autosectionlabel.saip-tool',
     'autosectionlabel.shell',
     'autosectionlabel.smpp2sim',