## What changes were proposed in this pull request?
This patch introduces three new annotations under InterfaceStability:
- Stable
- Evolving
- Unstable

This is inspired by Hadoop's InterfaceStability, and the first step towards switching over to a new API stability annotation framework.

## How was this patch tested?
N/A

Author: Reynold Xin <rxin@databricks.com>

Closes #15374 from rxin/SPARK-17800.