Add rule to prevent imports on Guava

This commit makes sure that we don't import a class from the Guava
library by mistake as it provides various utility classes with similar
names as our own.

Closes gh-10089

spring-boot-parent/src/checkstyle/checkstyle.xml

@@ -72,7 +72,9 @@
 			<property name="excludes"
 				value="org.assertj.core.api.Assertions.*, org.junit.Assert.*, org.junit.Assume.*, org.junit.internal.matchers.ThrowableMessageMatcher.*, org.hamcrest.CoreMatchers.*, org.hamcrest.Matchers.*, org.springframework.boot.configurationprocessor.ConfigurationMetadataMatchers.*, org.springframework.boot.configurationprocessor.TestCompiler.*, org.springframework.boot.test.autoconfigure.AutoConfigurationImportedCondition.*, org.mockito.Mockito.*, org.mockito.BDDMockito.*, org.mockito.ArgumentMatchers.*, org.mockito.Matchers.*, org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.*, org.springframework.restdocs.hypermedia.HypermediaDocumentation.*, org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*, org.springframework.test.web.servlet.result.MockMvcResultMatchers.*, org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.*, org.springframework.security.test.web.servlet.setup.SecurityMockMvcConfigurers.*, org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo, org.springframework.test.web.client.match.MockRestRequestMatchers.*, org.springframework.test.web.client.response.MockRestResponseCreators.*" />
 		</module>
-		<module name="com.puppycrawl.tools.checkstyle.checks.imports.IllegalImportCheck" />
+		<module name="com.puppycrawl.tools.checkstyle.checks.imports.IllegalImportCheck" >
+			<property name="illegalPkgs" value="com.google.common"/>
+		</module>
 		<module name="com.puppycrawl.tools.checkstyle.checks.imports.RedundantImportCheck" />
 		<module name="com.puppycrawl.tools.checkstyle.checks.imports.UnusedImportsCheck">
 			<property name="processJavadoc" value="true" />