Add Metadata caching in admin.internals.PartitionLeaderStrategy

Hi team,

To the best of my knowledge, there is no Metadata caching in AdminClient admin.internals.PartitionLeaderStrategy, and for use cases that keep long live AdminClient running with scheduled invocation of method such as the listOffsets, we could keep reusing the same Metadata and not request fresh one on each invocation

This is particularly true when the listOffsets is invoked for monitoring purpose, often querying a high number of partitions at the same time, leading to rather "large" Metadata requests to be processed on the cluster side

Thank you