ALTER INDEX to allow for STORING Clause

**Is your feature request related to a problem? Please describe.**

Currently, when I need to add one additional column to `STORING` clause an entire new index must be created and the old one removed.

**Describe the solution you'd like**

Support syntax like: `ALTER INDEX ... STORING( )` to include a different set of columns.

**Additional context**

It would also be great if we had a `STORING` *all* clause to include all columns in the table. As described here... https://github.com/cockroachdb/cockroach/issues/79105

Also, to have this automatically add columns when an `ALTER TABLE ADD COLUMN` command is run.

related: https://github.com/cockroachdb/cockroach/issues/111380

Jira issue: CRDB-25514

Epic CRDB-60817