Fix structlog configuration fails with dict input

[Kabir1618]

Summary

• Fix KeyError when stdlib logging passes a single dict argument through structlog (e.g. logging.warning('msg %s', {'a': 10}))
• CPython's LogRecord.__init__ unwraps single-dict args into a bare dict, but structlog's PositionalArgumentsFormatter expects a tuple and crashes when indexing it
• Add _normalize_positional_args processor that re-wraps bare dict args back into a tuple before PositionalArgumentsFormatter processes them

Closes #62201

Test plan

• Added 5 new tests in TestStdlibDictArgs covering: %s with dict, named %(key) formatting, empty dict, multi-key dict, and normal positional args
• All 39 tests in test_structlog.py pass (34 existing + 5 new)
• Manually verified the reproduction script from the issue works after the fix

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[justinpakzad]

I think there's already a PR for this issue: #62258

[Kabir1618]

The other PR has failing tests.

[SakshamSinghal20]

The other PR has failing tests.

@Kabir1618 That doesn't mean that the content is wrong if the maintainer has a problem with it i ll do the necessary changes.