adds additional augmented assignment statements (#4315)

[sarah-weatherbee]

Resolves issue #4315 by adding augmented assignment statements to:
core/dbt/dataclass_schema.py
core/dbt/graph/selector_spec.py
core/dbt/parser/manifest.py
test/integration/047_dbt_ls_test/test_ls.py
test/unit/test_macro_calls.py

Checklist

• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have updated the CHANGELOG.md and added information about my change

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[emmyoop]

@cla-bot check

[cla-bot]

Thanks for your pull request, and welcome to our community! We require contributors to sign our Contributor License Agreement and we don't seem to have your signature on file. Check out this article for more information on why we have a CLA.

In order for us to review and merge your code, please submit the Individual Contributor License Agreement form attached above above. If you have questions about the CLA, or if you believe you've received this message in error, don't hesitate to ping @drewbanin.

CLA has not been signed by users: @sarah-weatherbee

[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!

[emmyoop]

Once you get the CLA signed, you'll also want to add a line to the CHANGELOG.md for your change as well as add yourself to the contributors list. Looks like you'll be the first contributor for the next release so you can add that section!

[emmyoop]

Looks great! Thanks for helping make dbt-core better! Excited to work with you on more contributions!