ResourcesClassLoader does not participate in CGLIB's cache

[snicoll]

When a test is modified to automatically include resources as introduced by #44444, a classloader is introduced that doesn't implement SmartClassLoader. As a result, any CGLIB proxy that's created by that test will not be recorded correctly.

This looks to test failures when a second test attempt to load the same proxy:

Caused by: java.lang.LinkageError: loader 'app' attempted duplicate class definition for org.springframework.boot.autoconfigure.graphql.security.GraphQlWebFluxSecurityAutoConfigurationTests$BookService$$SpringCGLIB$$0. (org.springframework.boot.autoconfigure.graphql.security.GraphQlWebFluxSecurityAutoConfigurationTests$BookService$$SpringCGLIB$$0 is in unnamed module of loader 'app')
    at java.base/java.lang.ClassLoader.defineClass0(Native Method)
    at java.base/java.lang.System$2.defineClass(System.java:2324)
    at java.base/java.lang.invoke.MethodHandles$Lookup$ClassDefiner.defineClass(MethodHandles.java:2439)
    at java.base/java.lang.invoke.MethodHandles$Lookup$ClassDefiner.defineClass(MethodHandles.java:2416)
    at java.base/java.lang.invoke.MethodHandles$Lookup.defineClass(MethodHandles.java:1843)
    at org.springframework.cglib.core.ReflectUtils.defineClass(ReflectUtils.java:527)