RecompilableScriptFunctionData instances have gotten pretty big. There are some opportunities for reducing their footprint:

- most functions have empty nestedFunctions. Canonicalizing them with Collections.emptyMap() would help.
- most functions have empty internalSymbols. Canonicalizing them with Collections.emptySet() would help.
- most functions (those that don't set any this.* properties) will have the same allocatorClassName (JO4, currently) and an empty allocatorMap. By extracting the tuple of (allocatorClassName, allocatorMap, allocator) into a separate small AllocatorStrategy class and keeping a canonical DEFAULT_STRATEGY instance around for representing allocator strategy for functions that don't initialize any this.* properties, we could eliminate 2 fields, and reduce the number of class names and empty property maps around.