In odoo/documentation-user#945, the developer documentation is merged
with the user documentation in a single repository and build config.

This commit then removes source files for the developer documentation
from the odoo/odoo repository.

DOC PR: https://github.com/odoo/documentation-user/pull/945

task-2351938
task-2352371
task-2205684
task-2352544

Co-authored-by: Victor Feyens <vfe@odoo.com>
Co-authored-by: Antoine Vandevenne <anv@odoo.com>

Odoo no longer supports python 2, thus some of these helpers can and
have been replaced by python 3 built-ins, therefore there is no need for
them to stay defined.

The removed helpers are:
    * izip, imap and ifilter
    * unichr, text_type
    * implements_to_string, implements_iterator
    * string_types, integer_types
    * to_native

The python 2 shims have also been removed, and only the python 3 helpers
have been kept, because they can still be usable (i.e. accepting
both bytes and str for functions that can only accept one of the two)

[REM] pyjsparser: remove PY3 shims

They're no longer necessary as Odoo doesn't officially support python 2
anymore.

closes odoo/odoo#28519

* fix P3 incompatibilities in doc/_extensions
* vendor pyjsdoc, strip out everything we're not using and make what's
  left P3-compatible (upstream is not P3 compliant)
* drop undeclared dependency on attrs as it turns out not to be much
  used

* Fix a bunch of ill-documented/incomplete/incorrect method docs
* add start of Sphinx extension to extract & integrate jsdoc into
  Sphinx documentation:

  - parse JS files (and don't blow up), uses a fork of pyjsparser as
    the project currently does not parse comments
  - extract cross-module dependency information
  - parse JsDoc comments using pyjsdoc and infer structure from code &
    jsdoc
  - ``ast`` CLI printing a simplified AST of the input files
  - ``dependencies`` creating a dependency graph of either all modules
    in the provided input files or the modules matching the specified
    filters (warning: will not work if missing dependencies),
    generates a .dot file
  - ``extractor`` generating a plain text module documentation (mix of
    rst and markdown styles, not anything formal)
* sphinx extension with an "automodule" directive taking a module name
  and generating the documentation for it