WIP: remember load/store sizes during graphs building

[man9ourah]

Hello..

Following up on our discussion in #232, here is a work in progress PR and I appreciate any feedbacks.

Especially in following:

• In addComplexConsForExt, I am trying to get the total size of each field. Apparently, only utilizing SymbolTableInfo::getTypeSizeInBytes return the size for the element itself but not if it was an array. So I wrote a lambda that calculates the size. but I feel there is an easier way? Please let me know.
• Due to my limited knowledge in SVF, I did not know how to get the size for quite a few of the invocations of addLoadEdge & addStoreEdge .. but I did left a comment there to point them out and I made the added argument optional for backward compatibility. Any advice here is appreciated.
• Finally, do we need to propagate this further to VFG? or PAG is the place for it?

Any feedback is welcomed :)

Thanks.