This leaves the code in ScriptLoader and ScriptLoadHandler a lot more readable.
ScriptBytecodeCompressedDataLayout and ScriptBytecodeDataLayout simplify
locating data in the ScriptLoadRequest bytecode buffer when compressing and
decompressing it.
The interface is still error-prone. For example, these classes don't check
that the returned pointers are within the bounds of the buffer.
Differential Revision: https://phabricator.services.mozilla.com/D145011
55ed1fd8f6