* Fix: gather() eagerly creates coroutines before scheduling them
AggregateProvider fans out Provider.get_tool() (and sibling calls) across
child providers via gather(*[p.get_tool(x) for p in providers]). The list
comprehension builds every coroutine up front, then gather()'s scheduling
loop hands them to an anyio task group one at a time. If that loop is
interrupted partway through - e.g. by pytest-timeout's SIGALRM-based
per-test timeout, which can fire between any two bytecode instructions,
unlike normal async cancellation - any coroutine not yet scheduled is
abandoned and silently garbage collected later, producing a "coroutine
'Provider.get_tool' was never awaited" warning attributed to whatever
unrelated test happens to be running when the GC gets to it.
Change gather() to take a single iterable consumed lazily, one awaitable
at a time, right before each is scheduled, and close any awaitable that
was just retrieved if scheduling it raises. Update call sites to pass
generator expressions instead of eagerly-built lists so coroutine
creation and scheduling stay tightly coupled.
* Close unscheduled awaitables from eager callers; make get_tasks lazy
* Fix async partial callables rejected by iscoroutinefunction (#3423)
Add `is_coroutine_function()` utility that unwraps `functools.partial`
before checking, and guard `isroutine` checks so partials aren't
misrouted through `__call__`.
* Also check asyncio.iscoroutinefunction in is_coroutine_function
