chore: make lambda integ tests synchronous

[philasmar]

Issue #, if available:
DOTNET-7298

Description of changes:

• Uncomment the Lambda integration tests that we commented out due to them failing in the release pipeline.
• Changed the external processes from async to sync to account for the tests that take way longer to execute in the release pipeline as opposed to locally. Each test was taking around 15 mins in the release pipeline as opposed to seconds locally. I didn't want to cap it due to the weird behavior of the tests in the pipeline.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[ashovlin]

Easier comparison from before we commented out the tests: 2bacb92...d1ed32d

[ashovlin]

Okay with this incremental approach to unblock the release pipeline.

I'm curious if you tried using pwsh like we do over in the Lambda repo?

• https://github.com/aws/aws-lambda-dotnet/blob/9a0d0b4e4da636cdf3453f17464fd3dc4b1a8bd3/Libraries/test/TestServerlessApp.IntegrationTests/IntegrationTestContextFixture.cs#L44-L45

I'm not aware of us encountering the issue over there (though those tests take pretty long so perhaps we never noticed).