trace_request_ctx type is too restrictive

[layday]

Describe the bug

As of #8620, the request method's trace_request_ctx parameter is typed as taking a Mapping[str, str]. A value of str seems like an odd restriction to impose and other types are used in the wild. Some examples:

• current_attempt is numeric: https://github.com/inyutin/aiohttp_retry/blob/ba2169891f5b32a5c59e48ca185dd8e68e44ded7/aiohttp_retry/client.py#L116
• url is most likely a yarl.URL: https://github.com/fsspec/ipfsspec/blob/350c565352c6615aceedbe5e452b06a79855b0d5/ipfsspec/async_ipfs.py#L44
• timing_event_ctx is a nested dictionary: https://github.com/WordPress/openverse/blob/d4e84652d8936db5a62137e2a032926e203b50a2/api/api/utils/image_proxy/extension.py#L69

To Reproduce

n/a

Expected behavior

That a wider type would be accepted.

Logs/tracebacks

n/a

Python Version

$ python --version
3.12.5

aiohttp Version

$ python -m pip show aiohttp
3.10.8

multidict Version

$ python -m pip show multidict
6.1.0

yarl Version

$ python -m pip show yarl
1.13.1

OS

macOS

Related component

Client

Additional context

No response

Code of Conduct

• I agree to follow the aio-libs Code of Conduct