Implement delete_objects method

[Copilot]

Adds delete_objects to both sync Client and async AsyncClient, implementing the S3 multi-object delete API (POST /{bucket}?delete).

Changes

• presigner.py: Add query_string param to sign_request_headers so ?delete= is included in the SigV4 canonical request
• _base.py: Add _prepare_delete_objects (XML body construction, Content-MD5, signing) and _parse_delete_objects_response (XML response parsing with namespace handling)
• client.py / aio/client.py: Add POST to _execute_request and public delete_objects method
• tests: Sync and async coverage for normal deletion, quiet mode, and parameter validation
• benchmarks: Added delete_objects benchmarks to all 4 benchmark test files (sync, sync CM, async, async CM)

XML values are escaped via xml.sax.saxutils.escape to prevent injection.

Usage

response = client.delete_objects(
    Bucket="mybucket",
    Delete={
        "Objects": [{"Key": "file1.txt"}, {"Key": "file2.txt"}],
        "Quiet": False,
    },
)
# response["Deleted"] -> [{"Key": "file1.txt"}, {"Key": "file2.txt"}]

Original prompt

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This section details on the original issue you should resolve

<issue_title>Implementente delete_objects method</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Implementente delete_objects method #11

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[chrisburr]

@copilot

• pre-commit needs fixing
• the delete call should be included in the benchmarking

[Copilot]

@copilot

• pre-commit needs fixing
  ...

Fixed in 66a629b:

• Applied ruff format fixes for line length violations in source files; pre-commit now passes cleanly
• Added delete_objects benchmarks to all 4 benchmark files (test_benchmark.py, test_benchmark_cm.py, test_benchmark_aio.py, test_benchmark_aio_cm.py)