Migrate all tests to JUnit Jupiter

[tumbarumba]

Hamcrest, as a long lived project, has an large amount of tests written in different versions of JUnit, ranging from JUnit 3 styles tests that extend org.junit.TestCase, to other tests that are annotated with org.junit.Test. This change migrates all tests to use JUnit Jupiter, so that is all tests are now annotated with org.junit.jupiter.api.Test.

In most cases, this is a simple change of imports, with a few exceptions:

• Uses of assertTrue have been adjusted to allow for the description being the last parameter
• org.hamcrest.AbstractMatcherTest has been moved to org.hamcrest.test.AbstractMatcherTest
• Static assertion methods in AbstractMatcherTest have been moved to org.hamcrest.test.MatcherAssertions