Remove Powermock

Powermock does not support JUnit5 yet, so we need to remove it
to support JUnit 5. Additionally, maintaining additional libraries
adds extra work for the team.

Mockito now supports final classes and static method mocking. This
commit replaces Powermock with mockito-inline.

Closes gh-6025

web/spring-security-web.gradle

@@ -23,10 +23,11 @@ dependencies {
 	testImplementation 'commons-codec:commons-codec'
 	testImplementation 'io.projectreactor:reactor-test'
 	testImplementation 'javax.xml.bind:jaxb-api'
+	testImplementation 'org.mockito:mockito-core'
+	testImplementation 'org.mockito:mockito-inline'
 	testImplementation 'org.skyscreamer:jsonassert'
 	testImplementation 'org.springframework:spring-webflux'
 	testImplementation 'org.synchronoss.cloud:nio-multipart-parser'
-	testImplementation powerMock2Dependencies
 
 	testRuntimeOnly 'org.hsqldb:hsqldb'
 }