Add CambriansVSR/VSC/VSCStreaming model integrations

[akawincent]

Summary

• add cambrians_vsr as a new model integration
• add cambrians_vsc and cambrians_vsc_streaming as new model integrations
• add a Qwen2 cache-management monkey patch used by the Cambrian variants
• The above models all belong to the Cambrians' predictive sensing paradigm for efficiently processing ultra-long videos understanding. Ref: Cambrians Tech Report

In scope

• register cambrians_vsr, cambrians_vsc, and cambrians_vsc_streaming in lmms_eval.models
• add the three model implementations under lmms_eval/models/simple/
• add lmms_eval/models/model_utils/cambrians/qwen2_monkey_patch.py
• apply black/isort formatting required by repo lint

Out of scope

• benchmark/task additions
• environment setup or dependency changes
• evaluation script changes outside these model integrations

Validation

• pre-commit run --files lmms_eval/models/init.py lmms_eval/models/model_utils/cambrians/qwen2_monkey_patch.py lmms_eval/models/simple/cambrians_vsc.py lmms_eval/models/simple/cambrians_vsc_streaming.py lmms_eval/models/simple/cambrians_vsr.py | result: pass
• python -m lmms_eval models --aliases | rg cambrians(_vsc|_vsr|_vsc_streaming)? | result: pass

Risk / Compatibility

• low to medium risk: this adds new model backends and patches Qwen2 attention/cache behavior used by these Cambrian variants
• no intended behavior changes for unrelated model integrations

Type of Change

• Bug fix (non-breaking change)
• New feature
• New benchmark/task
• New model integration
• Breaking change
• Documentation update
• Refactoring (no functional changes)

[Luodian]

LGTM — monkey patch is scoped to Cambrians models only, no global side effects. Pairs with the already-merged VSI-SUPER benchmark (#1267).