KAFKA-19133: Support fetching for multiple remote fetch topic partitions in a single share fetch request (apache#19592)

### About
This PR removes the limitation in remote storage fetch for share groups
of only performing remote fetch for a single topic partition in a share
fetch request. With this PR, share groups can now fetch multiple remote
storage topic partitions in a single share fetch request.

### Testing
I have followed the [AK

documentation](https://kafka.apache.org/documentation/#tiered_storage_config_ex)
to test my code locally (by adopting `LocalTieredStorage.java`) and
verify with the help of logs that remote storage is happening for
multiple topic partitions in a single share fetch request. Also,
verified it with the help of unit tests.

Reviewers: Jun Rao <junrao@gmail.com>, Apoorv Mittal <apoorvmittal10@gmail.com>

Author: adixitconfluent