Moving comfy_torch_device into _execution_helpers put a top-level torch
import there, which broke the standard-library test run in CI. torch is
now imported inside that one function, and its tests skip where torch is
absent.
Four helper modules each carried their own _raise_if_interrupted, three
their own _progress_bar and three their own _warn_once, and Frame
Interpolate borrowed comfy_torch_device from LaMa's module.
_execution_helpers now holds one copy of each and the helpers import
them, with the old behavior kept exactly: progress_bar is the plain bar
those loops always built (unlike frame_progress it has no guard for
unknown totals), and warn_once takes each module's own seen-set, key
and cap (none for the stitch, 64 for presets, 256 for colors).
ausboss