[SPARK-17974] Refactor FileCatalog classes to simplify the inheritance tree

## What changes were proposed in this pull request?

This renames `BasicFileCatalog => FileCatalog`, combines  `SessionFileCatalog` with `PartitioningAwareFileCatalog`, and removes the old `FileCatalog` trait.

In summary,
```
MetadataLogFileCatalog extends PartitioningAwareFileCatalog
ListingFileCatalog extends PartitioningAwareFileCatalog
PartitioningAwareFileCatalog extends FileCatalog
TableFileCatalog extends FileCatalog
```

cc cloud-fan mallman

## How was this patch tested?

Existing tests

Author: Eric Liang <ekl@databricks.com>

Closes #15518 from ericl/refactor-session-file-catalog.