fix(asyncio): Keep an eager task factory recognizable as eager - #7710

Description

AsyncioIntegration wraps the loop's task factory in a plain function. When the original is an eager task factory, libraries can no longer tell: asyncio has no public way to ask, so anyio compares factory.__code__ with the standard library's. anyio then starts a task group's child eagerly, and the task group fails with Attempted to exit a cancel scope that isn't the current tasks's current cancel scope.

When the original factory is eager, the integration now installs one built with asyncio.create_eager_task_factory() and wraps the coroutine in its task constructor. The task is created with the original factory's constructor, read from its closure, because before Python 3.14 the eager factory does not accept eager_start. If the closure is not what is expected, the integration falls back to the plain wrapper. When a library calls the task constructor directly, as anyio does, the constructor sets the task's name itself, because no create_task() follows to apply it.

Issues

• resolves: AsyncioIntegration hides an eager task factory from anyio, which breaks anyio task groups #7709