[SPARK-13459][WEB UI] Separate Alive and Dead Executors in Executor Totals Table

## What changes were proposed in this pull request?

Now that dead executors are shown in the executors table (#10058) the totals table is updated to include the separate totals for alive and dead executors as well as the current total, as originally discussed in #10668

## How was this patch tested?

Manually verified by running the Standalone Web UI in the latest Safari and Firefox ESR

Author: Alex Bozarth <ajbozart@us.ibm.com>

Closes #11381 from ajbozarth/spark13459.