Deprecate `bedrock` instrumentation package once new instrumentation in `opentelemetry-python-genai` is ready

We have started instrumenting bedrock in the new optentelemetry-python-genai repo.

Once that library reaches parity with the one in this repo, we can deprecate the one here.

Proposal for how to deprecate:

Add a deprecation warning:

class _BedrockExtension:
    def __init__(self, ...):
        warnings.warn(
            "The Bedrock extension in 'opentelemetry-instrumentation-botocore' is deprecated "
            "and will be removed in a future release. "
            "Please use 'opentelemetry-instrumentation-genai-bedrock' instead.",
            category=DeprecationWarning,
            stacklevel=2,
        )

Disable BedrockExtension if opentelemetry-instrumentation-genai-bedrock is installed and enabled:

def _is_genai_bedrock_active() -> bool:
    if importlib.util.find_spec("opentelemetry.instrumentation.genai.bedrock") is None:
        return False
    try:
        from opentelemetry.instrumentation.genai.bedrock import BedrockInstrumentor
        return BedrockInstrumentor().is_instrumented_by_opentelemetry
    except Exception:
        return False
class _BedrockExtension:
    def __init__(self, ...):
        self._disabled = _is_genai_bedrock_active()
        if self._disabled:
            logger.debug(
                "opentelemetry-instrumentation-genai-bedrock is active; "
                "suppressing botocore BedrockExtension to avoid duplicate spans."
            )
    def extract_attributes(self, ...):
        if self._disabled:
            return  # No-op: let the new instrumentor handle GenAI telemetry
        ...

Update the README that gets pushed to PyPi to point people to the new instrumentation..

I think at that point we can delete the code here entirely.

Start by reviewing opentelemetry-python-genai PR 359 and checking whether its Bedrock instrumentation has reached parity. Then locate the existing BedrockExtension and the README published to PyPI; done means the deprecation and duplicate-instrumentation behavior are addressed and the README points users to the new package, with deletion confirmed if appropriate.