feat: Add Milvus Vector Database Implementation

[franciscojavierarceo]

What this PR does / why we need it:

This PR introduces the Milvus Vector Database into Feast. This integration enhances the capability of Feast to handle and store vector embeddings, along with traditional features. More specifically, this allows for vector retrieval configurable at the feature-level.

1. .github/workflows/pr_local_integration_tests.yml

• Updated test cache key

2. Makefile

• Added milvus makefile target

3. docs/how-to-guides/customizing-feast/adding-support-for-a-new-online-store.md

• Updated to remove path

4. sdk/python/docs/source/feast.infra.online_stores.milvus_online_store.rst

• Updated sphinx docs

5. sdk/python/feast/infra/online_stores/milvus_online_store/milvus.py

• Added Milvus online store implementation

6. sdk/python/feast/repo_config.py

• Added milvus to config

7. sdk/python/feast/type_map.py

• Updated _proto_value_to_value_type function

8. sdk/python/tests/foo_provider.py

• Updated requested_features as Optional

9. sdk/python/tests/integration/online_store/test_universal_online.py

• Added specific Milvus test...will likely remove later

Which issue(s) this PR fixes:

#4364

Misc

Will add docs in subsequent PR

[tchughesiv]

@franciscojavierarceo as we add support for additional data store types, should we encourage devs to update the operator db store types accordingly as well? or should we treat that as a separate chore since the dev language is different?

feast/infra/feast-operator/api/v1alpha1/featurestore_types.go

Line 161 in 19424bc

// +kubebuilder:validation:Enum=snowflake.online;redis;ikv;datastore;dynamodb;bigtable;postgres;cassandra;mysql;hazelcast;singlestore

feast/infra/feast-operator/api/v1alpha1/featurestore_types.go

Lines 169 to 181 in 19424bc

	var ValidOnlineStoreDBStorePersistenceTypes = []string{
	"snowflake.online",
	"redis",
	"ikv",
	"datastore",
	"dynamodb",
	"bigtable",
	"postgres",
	"cassandra",
	"mysql",
	"hazelcast",
	"singlestore",
	}

looking at the python code, it appears we need to add several more supported types to the operator.

[franciscojavierarceo]

@franciscojavierarceo as we add support for additional data store types, should we encourage devs to update the operator db store types accordingly as well? or should we treat that as a separate chore since the dev language is different?

feast/infra/feast-operator/api/v1alpha1/featurestore_types.go

Line 161 in 19424bc

// +kubebuilder:validation:Enum=snowflake.online;redis;ikv;datastore;dynamodb;bigtable;postgres;cassandra;mysql;hazelcast;singlestore

feast/infra/feast-operator/api/v1alpha1/featurestore_types.go

Lines 169 to 181 in 19424bc

	var ValidOnlineStoreDBStorePersistenceTypes = []string{
	"snowflake.online",
	"redis",
	"ikv",
	"datastore",
	"dynamodb",
	"bigtable",
	"postgres",
	"cassandra",
	"mysql",
	"hazelcast",
	"singlestore",
	}

looking at the python code, it appears we need to add several more supported types to the operator.

Definitely. We can add an explicit test for it too and update the docs. I can do that in a separate PR after I get this thing wrangled.

I'm still only partially through this and I still have quite a bit of work to do.

[shuchu]

lgtm