PIPE-3253: support telescope-specific cell determination via heuristics
- Add uniform_band_cell property to ImageParamsHeuristics (True for ALMA, False for VLA/VLASS).
- Update makeimlist Pass 1 to compute shared band-wide default cells only when uniform_band_cell is enabled.
- Update makeimlist Pass 2 to maintain independent per-field cell calculation for VLA/VLASS while preserving ALMA uniform in-band cells and size mitigation overrides.
