Add partitioned tables support

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Allows for subscribing to partitions of a partitioned table (which you could already do) but also subscribing to the root, partitioned, table and receiving all updates across all partitions.

Fixes #2118

Major changes:

• Add support for partitioned table types in the various inspector queries
• Include partition hierarchy information in relation information from pg and in inspector relation info
• Force reload of table information when receiving a new relation that is a partition
• Add partition information to Filter so that it can correctly pass on a change on a partition table to a shape on the partition root.
• For a shape subscribed to the partition root, changes coming in on partitions will be re-written so that their relation matches the partition root. The change keys are not being re-written - I don't think this is an issue as the keys are guaranteed to be unique and that's enough.
• Relation messages notifying of a new partition table are forwarded onto root-partition consumers so the shape can be updated with knowledge of the new partition (this does not cause the shape to be deleted)
• I've added a full-stack test to verify this stuff so that we're not making assumptions about pg's handling of partitions

Minor:

• support querying the inspector based on the {schema, name} relation tuple, as well as the table name string because I needed to be able to look up table info based
• Filter instances now have an inspector instance so they can do table info lookups to get partition information
• The filter functions used by the dispatcher now return {filter, shape_ids} so that the filter's state can be updated
• I've tweaked StubInspector so we can return richer info from the load_relation call
• Added missing serialisation of a shape's replica setting

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