[BUG] Prevent using operator names as metadata keys

[priyankc]

Description of changes

Fixes chroma-core#4388

In chromadb/api/types.py:

• Added a RESERVED_OPERATORS constant that lists all operator names that are reserved
• Updated validate_metadata() to check metadata keys against this list and reject any that match
• Added validation to prevent metadata keys starting with $ to avoid future conflicts

In chromadb/segment/impl/metadata/sqlite.py:

• Updated _where_map_criterion() to explicitly check for $in and $nin operators at the top level
• Added specialized handling for these operators to ensure they're properly processed

Test plan

python test_reproduce/test_complex_operator_bug.py

• Above returns wrong results without the patch
• With the fix, we throw an exception rejecting RESERVE_WORDS as keys

Scenario Represented in the Test Case

1. Create a collection with documents that have metadata keys matching operator names:

   client = chromadb.Client()
   collection = client.create_collection("test_collection_complex")
   collection.add(
       ids=["id1", "id2", "id3", "id4"],
       documents=["doc1", "doc2", "doc3", "doc4"],
       metadatas=[
           {"$in": "value1", "category": "A"},           # Has a key that matches operator
           {"category": "A", "tag": "special"},          # Normal metadata, category A
           {"$in": "value3", "category": "B"},           # Has a key that matches operator, different category
           {"category": "B", "tag": "special"}           # Normal metadata, category B
       ]
   )

2. Execute a complex query that uses $in both as a metadata key name and as an operator in different parts of the where clause:

   result = collection.get(
       where={"$and": [
           {"$in": "value3"},                # Using $in as a metadata key
           {"category": "B"},                # Regular filter
           {"tag": {"$in": ["special"]}}     # Using $in as an operator
       ]}
   )

3. Observe that the query returns no results, even though there should be a match (document with id4).

• Tests pass locally with pytest for python, yarn test for js, cargo test for rust

More details:

• RCA: https://hyperdrive.engineering/#report-8bac09ec-0e15-4bfd-b41e-21c4351c57aa
• Reproducing the Bug: https://gist.github.com/priyankc/d1e361470cbd74a896074c8d57641712

[hesreallyhim]

@priyankc FYI RCA link is saying "Report not found." not sure if just me/VPN