Document information about auto-restarts

There are certain cases where ColumnStore will automatically restart. For example, see MCOL-1161. For another example, ColumnStore will also auto-restart if the system is excessively swapping (I believe this swapping threshold is configurable).

These auto-restarts appear to be completely undocumented. We should probably create a new documentation page to document all of the cases where ColumnStore will automatically restart.

The page should probably also say what happens to queries that are running when the system auto-restarts. Are the queries killed and all uncommitted changes are rolled back?