[NewOp] Add domain_diversity_selector based on DaaR principles

[lingzhq]

Introduces a novel data selection op based on semantic diversity across domains, designed to automatically select the most diverse subset of data samples, which is inspired by the DaaR paper.

• Converts input samples into embeddings
• Use embeddings to cluster pseudo-domains
• Selects samples based on various distances to maximize diversity

[WIP] Ongoing development of additional operators derived from the DaaR.