AsyncAPI spec v3 support in Python paho template

[jonaslagoni]

Reason/Context

This Issue is used to track changes needed to support AsyncAPI v3. As a code owner, please edit this list of TODO tasks in order to properly track the progress 🙂 Once this issue is closed it means that v3 is now fully supported in this library.

Remaining tasks:

• Update template to use parser v2, this is already supported by the generator by changing the apiVersion

[github-actions]

Welcome to AsyncAPI. Thanks a lot for reporting your first issue. Please check out our contributors guide and the instructions about a basic recommended setup useful for opening a pull request.
Keep in mind there are also other channels you can use to interact with AsyncAPI community. For more details check out this issue.

[ItshMoh]

Hey, I need to tackle this issue in 2 seperate PRs one for converting it to use React engine and one for converting it to use v3 api. Right?

cc @jonaslagoni @derberg