[SPARK-3398] [EC2] Have spark-ec2 intelligently wait for specific cluster states

Instead of waiting arbitrary amounts of time for the cluster to reach a specific state, this patch lets `spark-ec2` explicitly wait for a cluster to reach a desired state.

This is useful in a couple of situations:
* The cluster is launching and you want to wait until SSH is available before installing stuff.
* The cluster is being terminated and you want to wait until all the instances are terminated before trying to delete security groups.

This patch removes the need for the `--wait` option and removes some of the time-based retry logic that was being used.

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #2339 from nchammas/spark-ec2-wait-properly and squashes the following commits:

43a69f0 [Nicholas Chammas] short-circuit SSH check; linear backoff
9a9e035 [Nicholas Chammas] remove extraneous comment
26c5ed0 [Nicholas Chammas] replace print with write()
bb67c06 [Nicholas Chammas] deprecate wait option; remove dead code
7969265 [Nicholas Chammas] fix long line (PEP 8)
126e4cf [Nicholas Chammas] wait for specific cluster states
[SPARK-3829] Make Spark logo image on the header of HistoryPage as a link to HistoryPage's page #1

There is a Spark logo on the header of HistoryPage.
We can have too many HistoryPages if we run 20+ applications. So I think, it's useful if the logo is as a link to the HistoryPage's page number 1.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2690 from sarutak/SPARK-3829 and squashes the following commits:

908c109 [Kousuke Saruta] Removed extra space.
00bfbd7 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into SPARK-3829
dd87480 [Kousuke Saruta] Made header Spark log image as a link to History Server's top page.