E3-core

* Add e3.pytest plugin to reuse fixtures in other projects
* Add support for VEX documents
* Update e3-pypi-closure to generate more precise version
* Enable Anod class to use methods instead of properties
* Ensure e3 is handled as a PEP 420 namespace
* Add secure_control_plane to anod

* Security enhancements:
* e3.net.smtp.sendmail uses to ``SMTP_SSL`` by default

* New Anod API Version 1.6:
* For performance issues declare dynamically "spec" function in the
Anod spec context rather than using e3.anod.loader.spec function
that relies on inspect module

* Add rlimit binary for aarch64-darwin

* Add support for M1/M2 MacOS (aarch64-darwin platform)
* e3.diff.patch raise an exception if there is no file to patch
* Fix issue where anod download deps are not tracked
* Add a SPDX document generator
* Add an interface to NVD API

* Minor backward incompatible changes:
* the discrimiant ``is_virtual`` has been removed
* e3.anod.sandbox.SandBox now has a mandatory root_dir attribute
* AnodSpecRepositories spec_config should now subclass SpecConfig
* PlanContext now returns PlanActionEnv, a subclass of BaseEnv. Contrary
to the previous BaseEnv objects, returned PlanActionEnv always have
the following attributes set: "push_to_store", "default_build",
"module", "source_packages"