Fix checkstyle import regex patterns

Update checkstyle rules to fix import regex patterns for both packages
and classes.

Author: philwebb

src/checkstyle/checkstyle.xml

@@ -3,9 +3,13 @@
 <module name="com.puppycrawl.tools.checkstyle.Checker">
 	<module name="io.spring.javaformat.checkstyle.SpringChecks" />
 	<module name="com.puppycrawl.tools.checkstyle.TreeWalker">
-		<module name="com.puppycrawl.tools.checkstyle.checks.imports.IllegalImportCheck">
-			<property name="illegalPkgs" value="sun, org.apache.commons.(?!compress|dbcp2|lang|lang3|logging|pool2).*, com.google.common, org.flywaydb.core.internal, reactor.core.support.Assert"/>
-			<property name="regexp" value="true"/>
+		<module
+			name="com.puppycrawl.tools.checkstyle.checks.imports.IllegalImportCheck">
+			<property name="regexp" value="true" />
+			<property name="illegalPkgs"
+				value="^sun.*, ^org\.apache\.commons\.(?!compress|dbcp2|lang|lang3|logging|pool2).*, ^com\.google\.common.*, ^org\.flywaydb\.core\.internal.*" />
+			<property name="illegalClasses"
+				value="^reactor\.core\.support\.Assert" />
 		</module>
 	</module>
 </module>