Fix LoaderUtil saying there are duplicate classpath entries if there are in fact none.

[Gamebuster19901]

Also futureproofs the checks just in case the class names are changed.

I was encountering issues with org.objectweb.asm.Type being loaded by both the knot classloader, and the app class loader. I removed ASM entirely and was thoroughly confused that the error message stated that were duplicate ASM classes.

Related to #965

Previous output if no ASM is on the classpath:

Exception in thread "main" java.lang.ExceptionInInitializerError
	at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)
Caused by: java.lang.IllegalStateException: duplicate ASM classes found on classpath: 
	at net.fabricmc.loader.impl.util.LoaderUtil.verifyClasspath(LoaderUtil.java:71)
	at net.fabricmc.loader.impl.launch.knot.Knot.<clinit>(Knot.java:345)
	... 1 more

New output if no ASM is on the classpath:

Exception in thread "main" java.lang.ExceptionInInitializerError
	at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)
Caused by: java.lang.IllegalStateException: ASM not detected on the classpath (or perhaps org/objectweb/asm/ClassReader.class was renamed?)
	at net.fabricmc.loader.impl.util.LoaderUtil.verifyClasspath(LoaderUtil.java:89)
	at net.fabricmc.loader.impl.launch.knot.Knot.<clinit>(Knot.java:345)
	... 1 more