Fix ThrowableProxy unit tests

Modified the regex patterns in RootCauseFirstThrowableProxyTest and
ExtendedThrowableProxyTest to find any packaging info in the throwable's
stack trace, including inexact matches.

On Cloudbees Jenkins, these tests were failing because they were looking
for an exact match of the JUnit package but only found an inexact one.

(cherry picked from commit dcfb0a056f3e084d8395b33f4d4acdb5d7ea7dba)
Fix RecoveryCoordinatorTest

Use new instance of RecoveryCoordinator in each test. Otherwise, the timestamp
of the next call to isTooSoon() could happen well after the backoff threshold
on slow machines (such as small nodes on Cloudbees Jenkins), causing false
test failures.

This also renames and refines the individual tests.

(cherry picked from commit 409ba25961d40b4a6f7268ea596190a1abd4b935)