filterV2 schema narrowed; filter field removed; nullable removed from filter

Several breaking-leaning schema changes are present in this diff:

• filterV2 on log drain objects was previously a oneOf supporting both v1 and v2 filter versions; the v1 variant has been removed, narrowing the schema to only accept v2 filters. Clients sending version: "v1" will now fail validation.
• A top-level filter string field that existed alongside filterV2 has been removed entirely.
• A filter field in a separate oneOf union had its nullable: true constraint removed, which may break clients that rely on null being a valid value.
• projectFlagsSdkKey ACL action array is newly added across multiple role/permission response schemas — this is a purely additive addition.