feat: support Vector Search

[pl04351820]

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This is new vector search feature support for Firestore:

• Support vector data type
  • Reordering the vector data type in SDK to be consistent with server.
  • Auto covert data type from int to double if it is a vector type.
• Support FindNearest for Query/Collection/CollectionGroup.
  • Support distance measurement with EUCLIDEAN/COSINE/DOT_PRODUCT.
  • Support pre-filter with equality condition.

Testing:

• Unit and System tests coverage on vector data and vector query.
• A util script to bootstrap vector index for system tests.

Future Work: Async vector search support and error handling with retry will come in follow-up PR

[parthea]

LGTM but waiting to formally approve until we determine if there is a breaking change