test: cover resuming engine with unknown epoch length

[nightcityblade]

Fixes #1331

Description:

Adds regression coverage for continuing an engine after terminate() when the data iterator has unknown epoch_length.

Check list:

• New tests are added (if a new feature is added)
• New doc strings: description and/or example code are in RST format
• Documentation is updated (if required)

[vfdev-5]

@nightcityblade resolve the conflict with master branch

[nightcityblade]

Rebased fix/issue-1331 on current master and resolved the import conflict in tests/ignite/engine/test_engine.py by keeping both itertools and the current master imports.

Validation run:

• python3 -m pytest tests/ignite/engine/test_engine.py::TestEngine::test_continue_after_terminate_with_unknown_epoch_length -q — 2 passed
• python3 -m ruff check tests/ignite/engine/test_engine.py — passed

[vfdev-5]

Suggested change

	assert state.epoch == 2
	# TODO: engine bug that increments the epoch counter: https://github.com/pytorch/ignite/issues/1386
	# Uncomment the check when fixed
	# assert state.epoch == 1

[nightcityblade]

Addressed the inline suggestion in commit 4ebadba: I replaced the first state.epoch assertion with a TODO referencing the known engine epoch-counter bug in #1386, while keeping the regression coverage for iteration and unknown epoch_length. Validation rerun: python3 -m pytest tests/ignite/engine/test_engine.py::TestEngine::test_continue_after_terminate_with_unknown_epoch_length -q and python3 -m ruff check tests/ignite/engine/test_engine.py.