fix(canvas): fire task lifecycle hooks for map/starmap items - #10880

Description

Fixes #7585
Fixes #7586

The celery.map and celery.starmap builtin tasks ran each item by calling the task instance directly (task(item) / task(*item)), which skips the task trace completely. That means before_start, on_success, on_failure and after_return never fired for mapped items, and task signals were never sent, even though all of them fire for the same task executed on its own. chunks is affected too since it fans out through xstarmap.

The fix routes every item through Task.apply() so each one gets a full trace. .get(disable_sync_subtasks=False) is safe here: the EagerResult is already computed, so it never blocks, and passing False keeps this working inside real workers where the join guard is on. Exceptions still propagate out of the map task exactly as before, and now on_failure fires for them.

Repro (before the fix, map apply hooks was []):

from celery import Celery, Task

app = Celery('x', broker='memory://', backend='cache+memory://')
app.conf.task_always_eager = True

calls = []

class MyTask(Task):
    def before_start(self, task_id, args, kwargs):
        calls.append(('before_start', args))
    def after_return(self, status, retval, task_id, args, kwargs, einfo):
        calls.append(('after_return', status))

@app.task(base=MyTask)
def add1(x):
    return x + 1

add1.map([1, 2, 3]).apply()
print(calls)  # now: before_start/after_return per item

Tests: added regression tests in t/unit/app/test_builtins.py covering hook order per mapped item for map and starmap, plus on_failure firing when an item raises. Ran t/unit/app/test_builtins.py, t/unit/tasks/test_canvas.py, t/unit/app/test_trace.py, t/unit/tasks/test_result.py, t/unit/tasks/test_tasks.py: 638 passed, 1 skipped, 1 xfailed, all green.

Also fixes #7586: autoretry_for was ignored for mapped items because the retry logic lives in the trace path. Verified: a task with autoretry_for=(ValueError,) and max_retries=3 raised after a single attempt through map before this change; now each item retries independently.