Handle recoverable truncated image payloads

[rajantripathi]

Summary

• Allow PIL to load recoverable truncated image payloads in the central VLM image utilities.
• Add a regression test covering base64 TSV image decoding to a local file.

Why

Some benchmark TSVs can contain recoverable truncated PNG/JPEG payloads. In those cases, a whole evaluation combination should not fail when PIL can still decode and re-save the image.

Fixes #1400.

Tests

• python -m pytest tests/test_smp_vlm.py -q
• python -m py_compile vlmeval/smp/vlm.py tests/test_smp_vlm.py
• git diff --check