* Update a few plugins for Java 11 compatibility
Guice 5.0.1 is now compatible with Java 11. However we don't
directly depend on Guice. Rather Soy depends on Guice. So I added a
direct dependency on Guice 5.0 just before Soy in order to frontload Soy
and pull in the newer version.
Mockito 3.7.7 is now compatible with Java 11. The complication is that
we need to use the inline version of Mockito, which among other things
also allows mocking for final classes (hooray!). It will eventually
become the default Mockito mock maker but for now it needs to be
manually activated.
Note that the inline version now introduces another warning:
```
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
```
Which I think is WAI due to how the inline mock maker works. Waiting on
the author to confirm.
After these to changes the only illegal reflective access is caused by
App Engine SDK tools, which we will rid ourselves of when we migrate off
of GAE.
* Restore package-lock.json
* Get rid of all remaining JUnit 4 usages except in prober & proxy subprojects
Caveat: Test suites aren't yet implemented in JUnit 5 so we still use the ones
from JUnit 5 in the core subproject.
* Fix some build errors
This adds an entriesToImmutableMap() collector that can be used in place of
toImmutableMap(Map.Entry::getkey, Map.Entry::getValue()).
It also fixes up some existing calls that use toImmutableMap() when terser
alternatives exist.
