Fix bindlines on Python 3.10+ by using collections.abc.Iterable

[williamhsiao0403]

Summary

This fixes LineIterator.bindlines() on modern Python versions where collections.Iterable is no longer available.

bindlines() was still checking iterability via collections.Iterable, which raises AttributeError on Python 3.10+ when an indicator calls bindlines().

The change mirrors the compatibility pattern already used elsewhere in the codebase: use collections.abc when available, and fall back to collections for older Python versions.

Changes

• Use collections.abc.Iterable in LineIterator.bindlines()
• Keep backward compatibility with older Python versions
• Add a regression test for Indicator.bindlines()

Verification

Tested with Python 3.13.1:

python tests/test_lineiterator_bindlines.py
python -c "import test_ind_sma; test_ind_sma.test_run()"
python -c "import test_writer; test_writer.test_run()"
python -m compileall -q backtrader tests/test_lineiterator_bindlines.py