Add migration job resources

[simplylizz]

Add possibility to set resource limits and requests for airflow-migration-job.

[boring-cyborg]

Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contribution Guide (https://github.com/apache/airflow/blob/main/CONTRIBUTING.rst)
Here are some useful points:

• Pay attention to the quality of your code (flake8, mypy and type annotations). Our pre-commits will help you with that.
• In case of a new feature add useful documentation (in docstrings or in docs/ directory). Adding a new operator? Check this short guide Consider adding an example DAG that shows how users should use it.
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[boring-cyborg]

Awesome work, congrats on your first merged pull request!

[simplylizz]

https://github.com/apache/airflow/runs/3984371457?check_suite_focus=true#step:8:4114 - @mik-laj I see one test is failing after merging. Should I bother with it or they are just flaky?

[mik-laj]

It looks like a flaky test.