Firestore: add IN and ARRAY_CONTAINS_ANY query operators

[BenWhitehead]

With an upcoming backend up date Firestore will have support for two new query operators IN and ARRAY_CONTAINS_ANY. In order for these new operators to be used, they need to be wired up to the high level query system.

These new operators allow queries like the following:

// IN query
firestore.collection('cities')
    .where("country", 'in', ['USA', 'Japan'])

// ARRAY_CONTAINS_ANY
firestore.collection('cities')
   .where('regions', 'array-contains-any', ['west_coast', 'east_coast'])

Both operators expect an ArrayValue to match against.

Additional context

• New operators added to protos in googleapis/googleapis@10f91fa
• NodeJS reference implementation: feat: add IN queries support  nodejs-firestore#715

[tseaver]

@BenWhitehead For consistency with the existing spelling for the StructuredQuery.FieldFilter.Operator.ARRAY_CONTAINS operator enum in Python ("array_contains"), I think we should spell the ARRAY_CONTAINS_ANY operator as "array_contains_any" in Python.

[BenWhitehead]

Sounds good. Keeping with the convention is more important than matching the proto names I think.