Migrate to BDD Mockito

Migrate Mockito imports to use the BDD variant. This aligns better with
the "given" / "when" / "then" style used in most tests since the "given"
block now uses Mockito `given(...)` calls.

The commit also updates a few tests that were accidentally using
Power Mockito when regular Mockito could be used.

Issue gh-8945

etc/checkstyle/checkstyle-suppressions.xml

@@ -3,7 +3,6 @@
 		"-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN"
 		"https://checkstyle.org/dtds/suppressions_1_2.dtd">
 <suppressions>
-	<suppress files=".*" checks="RegexpSinglelineJava" />
 	<suppress files=".*" checks="SimplifyBooleanExpression" />
 	<suppress files=".*" checks="SimplifyBooleanReturn" />
 	<suppress files=".*" checks="SpringAvoidStaticImport" />