devtools/jiri-test: rewrite release metatest.
devtools/jiri-test: rewrite release metatest.

Change the procedure to the following:
- Prepare binaries.
- Update installations.
- Update mounttable and wait for it.
- Update non-mounttable apps.
- Update device manager.
- Health check.

Change the code structure so that it can be easily used for
releasing production services.

The output will look like this:
https://paste.googleplex.com/6051651030876160

I plan to test this for staging, and then add procedures for
production push.

Change-Id: Id804bed87eea87076ea454b01af499285bb5c52d

vanadium/go.devtools,vanadium/go.devtools,vanadium/go.devtools