feat: Adding DAG parsing profiler tool

[tiranux]

Description

Adding a new DAG tool to troubleshoot and profile DAGs parsing.

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.9 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• Please merge this PR for me once it is approved

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• composer/tools/parsing_profiler/dag_linter_kubernetes_pod.py:16, tag composer_dag_parsing_profiler_dag
• composer/tools/parsing_profiler/linter_core.py:16, tag composer_dag_linter_core

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[iennae]

leave this first line out, should start with copyright header.

[iennae]

This feels really long to be embedded in docs with this region tag. Are you expecting to add the full thing here based on the region tag?