Develop Mypy plugin to type-check XComArg passed to a template_field

[uranusjr]

Body

Task extracted from #25604 (review)

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• I acknowledge that I am a maintainer/committer of the Apache Airflow project.

[potiuk]

Comment. Would be great. Unfortunately developing MyPy plugin is not an easy task. The docs are very sparse :(

[josh-fell]

Addressed via #26023.