This is a followup pr to #174951

This pr is a combined work  from @sbidoul who proposed an alternative to pkg_ressource using packaging, removing dependency on pkg_ressource (witch is excellent)

Unfortunately, we don't want to add a requirement on packaging since it is not needed to run odoo by default. It should be only useful when defining a "complex" external dependency (with version or markers)

This pr proposes to replace` packaging.Requirement` by a simple replacement, that would work for basic external_dependencies. (no version or marker)

Note that another change was made to the original proposal to continue to support module name dependency (ex: PIL instead of Pillow, the distribution package name) but will log a warning in this case instead of the previous info. Still to discuss if we need to  keep it.

Note that a first version (see 4e9e5924f7254b470397b61573b7c634c654d61c) was trying to combine both logic in `check_python_external_dependency` but some code needed to be duplicated and a version proposing a similar api to Requirements allows a smaller change to the original pr.