Add support for shading

[adamthom-amzn]

It's currently not possible to shade aws-crt-java (rename its class files and native libraries and embed them into my own artifact). Renaming the class files itself works, but an UnsatisfiedLinkError is raised in software.amazon.awssdk.crt.CRT#awsCrtInit.

An ideal shading solution would allow for us to rename both the native libraries and the Java classes. As an example, Netty allows consumers to shade their classes and native libraries. They support a system property to allow customers to specify the prefix given to the libraries, though they later added support for automatically detecting the prefix. They also had to take special care to make sure multiple shaded versions of their library could coexist peacefully.