Reduce memory usage

This is a series of commits that reduce both CPU and memory usage of my simple test file, dynjs-spec/src/test/resources/suite/ch15/15.1/15.1.3/15.1.3.2. The memory usage is practically cut in half during the test run and the duration of the test went from 2.5 minutes on my machine to 1.75 minutes.

The number of loaded classes also decreased by about 150 due to removing the anonymous class usage for PropertyDescriptor and CodeBlock.