fix(psycopg): support async iteration [backport 2.9]

[github-actions]

Backport d51fa8d from #9940 to 2.9.

Motivation:

Previously, using async iteration with psycopg (async for) would throw an exception.

Example:

def connect_to_db():
    # db connection logic...

async def testfunc():
    connectstr = get_conn_str()
    async with AsyncConnectionPool(
        conninfo=connectstr, min_size=4, max_size=30
    ) as async_pool:
        async with async_pool.connection() as conn:
            async with conn.cursor() as cur:
                await cur.execute(
                    sql.SQL(
                        """
                        SELECT
                            *
                        FROM table1
                        LIMIT 5
                    """
                    )
                )
                async for row in cur:
                    print(row)

Running ddtrace-run python test.py would return TypeError: 'async for' requires an object with __aiter__ method, got Psycopg3TracedAsyncCursor.

This fix implements the __aiter__ method for the TracedAsyncCursor parent class, and has Psycopg3TracedAsyncCursor inherit from it.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, 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

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: backport-9940-to-2.9
Commit report: 880a6f0
Test service: dd-trace-py

✅ 0 Failed, 2876 Passed, 1666 Skipped, 34m 13.3s Total duration (21m 35.03s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-07-31 00:39:52

Comparing candidate commit c83b27c in PR branch backport-9940-to-2.9 with baseline commit d35198a in branch 2.9.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 209 metrics, 9 unstable metrics.