Add webjars-locator-lite, upgrading gradle build, and Replacing @MockBean

[patbaumgartner]

• Adding webjars-locator-lite and updating checkstyle version. This should give the pet clinic a startup boost by a bit.
• Gradle Build was processing AOT which led due to an issue in Spring Framework (Skip runtime hint registration for validation constraint with missing dependencies spring-framework#33949) to a build failure.
• Replacing @MockBean with @MockitoBean