test-libraries-for-java: add to Guava, migrate Guava off, or disband

[cpovirk]

Thanks to #1752 (comment), which points out that UninterruptiblesTest isn't part of Guava, I'm reminded that it's Google-internal because it uses TearDownTestCase, part of the old test-libraries-for-java.

Here are some internal-only links with context:

• https://goto.google.com/dktsv
• https://goto.google.com/imixm
• https://goto.google.com/kuapz
• https://goto.google.com/avwjj

The only TearDownTestCase users that ought to be released in Guava are:

• UninterruptiblesTest (and UninterruptibleFutureTest)

TearDownStack has two Guava users:

• AbstractExecutionThreadService
• MonitorTestCase

Possibly the Uninterruptibe* should just use TearDownStack manually, too?

[cpovirk]

I removed the usages from Uninterruptibles* in favor of manual usage of TearDownStack.

There's probably little urgency to do anything else here (and arguably the rest of the bug isn't about "Guava," anyway), so feel free to unassign and/or close.