GetEstimatedRangeSizeBytes can cause PacketLimitExceeded error on commit proxies

As reported [here](https://forums.foundationdb.org/t/packetlimitexceeded-error-on-stateless-servers/4188/15), if `GetEstimatedRangeSizeBytes` API uses a large key range, it can cause `PacketLimitExceeded` errors on commit proxies. This is because `getStorageMetricsLargeKeyRange()` invokes `getKeyRangeLocations()` to obtain location information for all shards within the specified key range. For a large range, the size of location information is unbounded and may exceed the packet size limit.

Start by reading GetEstimatedRangeSizeBytes, getStorageMetricsLargeKeyRange(), and getKeyRangeLocations() to trace how location information is gathered for a large range. Reproduce or inspect the PacketLimitExceeded path on commit proxies, then define completion as handling large ranges without exceeding the packet limit and verifying the behavior with regression coverage.

Written by the indexing model from the issue text.