feat: Add support for more recent versions of aiopg (closes #8229)

[wlach]

This PR updates the code to use new-style async/await, fixing compatibility with more recent versions of aiopg.

Checklist

• [ ] Change(s) are motivated and described in the PR description
• [ ] Testing strategy is described if automated tests are not included in the PR
• [ ] Risks are described (performance impact, potential for breakage, maintainability)
• [ ] Change is maintainable (easy to change, telemetry, documentation)
• [ ] Library release note guidelines are followed or label changelog/no-changelog is set
• [ ] Documentation is included (in-code, generated user docs, public corp docs)
• [ ] Backport labels are set (if applicable)
• [ ] If this PR changes the public interface, I've notified @DataDog/apm-tees.
• [ ] If change touches code that signs or publishes builds or packages, or handles credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.

Reviewer Checklist

• [ ] Title is accurate
• [ ] All changes are related to the pull request's stated goal
• [ ] Description motivates each change
• [ ] Avoids breaking API changes
• [ ] Testing strategy adequately addresses listed risks
• [ ] Change is maintainable (easy to change, telemetry, documentation)
• [ ] Release note makes sense to a user of the library
• [ ] Author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• [ ] Backport labels are set in a manner that is consistent with the release branch maintenance policy

[wlach]

Tested this out and verified that I got a trace for psycopg-style code when using aiopg (version 1.4.0). I will confess I am not an expert on datadog or its internals.

[wlach]

I think this is ready for a preliminary review. Please see comments for questions.

[ghthor]

@datadog anything blocking a review of this open PR?

[wlach]

Thank you @emmettbutler! Much appreciated ❤️