…lastic#59718)

This is a pre-cursor to elastic#58529

I realized a bit ago that we weren't making quite enough info available
in the action parameter templating that happens when alerts schedule
actions to execute.  Missing were alert name, tags, and spaceId.

For the index threshold alert, I had added them to it's context, but
then every other action would have to do the same if they also
wanted those values.

So I added these as additional top-level variables that can be
used in templates, along with the alert id, alert instance id,
context, and state.  The other bits in RawAlert didn't seem
that interesting, to be used as an action parameter.