Change Feed Processor: Adds support for EPK leases

[ealsur]

Description

This PR adds support for leases that represent a range of partition values and the wiring into the internal FeedProcessor to execute the Change Feed read based on the type of lease acquired by the Host.

The default lease schema is maintained as the current one (identified as Version 1) that maps 1 lease to 1 physical partition for backward compatibility with existing lease stores and V2 CFP.

When an event that affects the current partition (such as a partition Merge) happens, the current lease is migrated to the new schema.

This new schema versioning also prepares CFP to support decoupling the number of partitions from the number of leases, which will eventually let users define a higher degree of parallelization.

Lease schema difference

The current default (coming from V2 CFP) schema looks like:

{
    "id": "<some value>",
    "version": 0,
    "LeaseToken": "<partition id>",
    "Owner": "<instance name>",
    "ContinuationToken": "<continuation>",
    "properties": {},
    "timestamp": "<timestamp>"
}

The new range based lease's schema is:

{
    "id": "<some value>",
    "version": 1,
    "LeaseToken": "<range representation>",
    "FeedRange": {
        "Range": {
            "min": "<initial partition key value of the range>",
            "max": "<final partition key value of the range>"
        }
    },
    "Owner": "<instance name>",
    "ContinuationToken": "<continuation>",
    "properties": {},
    "timestamp": "<timestamp>"
}

Code changes details

• CFP code previously was using a ReadFeed on the partition key ranges to list partitions, instead of relying on the SDKs caches. We are now wiring down the caches to leverage them instead of doing independent calls.
• PartitionSynchronizer now has independent handling based on lease type/version, as the handling is now dependent on what does the lease represent (full partition or a range)
• FeedProcessor uses ChangeFeedPartitionKeyResultSetIteratorCore which now can set the EPK filter headers for leases that represent a range.
• Adding new sets of UTs to cover existing classes and new classes

Type of change

• New feature (non-breaking change which adds functionality)

[ghost]

Closing due to in-activity, pease feel free to re-open.