[Improvement] Add switch to load the latest schema for a external Lance table

### What would you like to be improved?

For an `external` Lance table, Users can operate the location directly, such as write data, schema change. Possibly out-of-date information will be retrieved when calling `loadTable` in the Lance REST service or the Gravitino API. So I propose to add a switch to fetch the latest schema information from the Lance storage when loading the table, in this case, users can stil fetch the latest metadata information.

### How should we improve?

_No response_

Start by tracing loadTable in the Lance REST service and the Gravitino API for external Lance tables. Determine where a switch can request the latest schema from Lance storage, then verify that loading after a direct schema change returns the current metadata.

Written by the indexing model from the issue text.