[DataFrame] _IndexMetadata.copy() may block on OID-backed _index_cache

[p-yang]

Describe the problem

Since we will support passing the index as an Object ID for _IndexMetadata as of #1984, _IndexMetadata.copy() may result in a blocking call waiting for _index_cache to be populated. Refer to the code snippet below.

Source code / logs

https://github.com/ray-project/ray/blob/master/python/ray/dataframe/index_metadata.py#L270

[devin-petersohn]

@Veryku Opening a new issue to track this on the Modin repo