docs: Update the ELF guides

Rewrite parts of the two ELF guides to use scripts included in the
export archive and modernize some deprecated tools and Bash idioms.

Also add the new sphinx_collapse extension to the docs build config.

Signed-off-by: Niccolò Maggioni <nicco.maggioni+nuttx@gmail.com>

Documentation/Pipfile

@@ -17,3 +17,4 @@ pytz = "*"
 importlib-metadata = "*"
 sphinx-tags = "*"
 sphinx-design = "*"
+sphinx-collapse = "*"

Documentation/conf.py

@@ -61,6 +61,7 @@ extensions = [
     "warnings_filter",
     "sphinx_tags",
     "sphinx_design",
+    "sphinx_collapse",
 ]
 
 source_suffix = [".rst", ".md"]