OTEL_PYTHON_CONTEXT not working

[WqyJh]

Environment

• Ubuntu 22.04
• Python 3.10.12

Steps to reproduce
Set OTEL_PYTHON_CONTEXT=context.

What is the expected behavior?
_RUNTIME_CONTEXT be initiated as an Context instance.

What is the actual behavior?
_RUNTIME_CONTEXT failed to initialize.

Additional context

If OTEL_PYTHON_CONTEXT=contextvars_context, an ContextVarsRuntimeContext instance would be loaded, however, if OTEL_PYTHON_CONTEXT=context, an Context instance won't be loaded. This is caused by entry_points function, the return value contains only one EntryPoint named contextvars_context.

See #3763 (comment)