Optimization: optimize shell to only read from catalog when there are changes

[ray6080]

Description

Currently, updateTableNames is called during shell startup and also inside processInput, basically each query can involve the read of tables from Catalog, which should be unnecessary and pose extra overheads when there are no changes inside Catalog.

One solution is to maintain a version in Catalog and check the version before reading from it. The other one is to sync from Catalog after processing of a fixed number of inputs. The former should be simple and preferable.