Add inline type annotations to dynamically generated modules

[Jun Komoda]

In #327, we were planning to implement a feature to generate a .pyi file with its type hints as soon as the module is generated by client.GetModule.

However, with a suggestion from @kdschlosser, we shifted to generating modules with inline type annotations.

Inline type annotations are only available in Python 3.x and later, so the merge destination for the contributions is drop_py2 branch.

As planned in #392, we will support Python3.7 and later versions, so type hinting should be done in the way supported from 3.7 and earlier.
For example...

• Literal (new in Python3.8), Final (new in Python3.8), Self (new in Python3.10), and other new symbols are not available.
• PEP585 is not available.
• PEP604 is not available.

This kanban will be updated as the situation requires.

Any opinions would be appreciated.