Update retrieval configs to use separate models

[danmichaeljones]

• Splits the RetrievalConfig model into separate models for each retrieval type, to make adding it easier to add extra parameters for one type only in future
• Adds the option to use a string for retrieval_config to simplify changing the retrieval type while keeping default parameters, e.g.,

results = client.memories.search(
    query="Tell me about the user",
    user_id=USER_ID,
    retrieval_config="hyrbid",
)

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[CShorten]

Nice, looks great -- curious about the slots parameter on dataclass, is this a memory allocation thing?