Resource Leak Checker consuming excessive memory for compilation unit

[msridhar]

Test case:
hive_parse_test.zip

To reproduce, unzip, and modify compile.sh so that CF_ROOT points to your local Checker Framework repo. Then run ./compile.sh. The checker exhausts 16GB of RAM analyzing HiveParser.java. It's a large (~30k lines) source file generated by ANTLR I think. But still, 16GB of heap for one file is a lot. Even just running the Tainting Checker on this class needs about 8GB of heap. The RLC is hurt by needing to run the MustCallChecker as a sub checker and keep its state in memory. Doing some memory profiling, it seems a significant amount of memory is consumed by the caching of flow analysis results in the org.checkerframework.framework.type.GenericAnnotatedTypeFactory#flowResult field.