Partial index using timestamp / mvcc_timestamp

**Is your feature request related to a problem? Please describe.**
Creating a full index on a large table may take a long time. In certain urgent cases, there is a need for the ability to quickly create a partial index using timestamps when only the latest data (up to 1 month) is required.

**Describe the solution you'd like**
The ability to quickly create a partial index using timestamps when only the latest data (up to 1 month) is required.

**Describe alternatives you've considered**
None at this time.

**Additional context**
N/A

Jira issue: CRDB-28848