Global pre-processing for leveraging callgraphs

[TilakMaddy]

CallGraphs can now be leveraged with help of StandardInvestigator - I have tried to make as many default assumptions as possible to keep the interface simple to use.

Job of the investigator is to derive a subgraph from the master workspace callgraph and provide hooks to interact with functions and modifiers while it does the following:

• Navigate upstream
• Navigate downstream
• Navigate upstream's downstream-side-effects (These are nodes that are downstream from the upstream nodes but are not upstream themselves)

PS: You can provide a navigation style to save time and be efficient in terms of covering traversal ground

Pre-processing

• The investigator relies on the callgraph to be present attached to workspace context.
• We create forward callgraph then, transpose (flip the edges) it to get a reverse callgraph (for upstream navigation)
• Then attach both to Workspace Context before the pipeline is run

Trackers

• These are structures that consume from the investigators and every detector that makes use of the investigator is expected to maintain it's own tracker for tracking stuff across procedure boundaries.
• Then this information is used to communicate back to the detector what to do about the investigation

Future scope

• Inter contract analysis ? 🧐

Add the following detectors as proof of concept to this PR

• Functions that send native eth without having msg.sender checks #597
• Controlled delegatecall destination check ! #600
• x.sub(y) without if checks to stop unexpected reverts (cc: @devdacian)

[TilakMaddy]

@alexroan There are bunch of unit tests for the callgraph framework in the file detect/experimental/cfg_sample.rs in addition to that the 3 detectors' tests :) In fact, I want to add more but I'll wait for your approval :)

[alexroan]

It feels like there are a few detectors and other features we're trying to squeeze in at once.
So that I know what I'm reviewing, could you reference all the tickets being addressed in this one please @TilakMaddy ?

[TilakMaddy]

@alexroan You are right, I was focussed on the callgraph library and I didn't even realize I used the same Tower.sol file for testing the detectors as well as the callgraph. I have now seperated them and also under relevant file names.

SendEtherNoChecks.sol and CallGraphTests.sol

[alexroan]

This is looking very good @TilakMaddy . I have a few change requests before another review. We're getting close though, this looks powerful af.

[alexroan]

I'm removing "Sub without If" from this so we can merge the callgraph without it blocking.

[alexroan]

Approved, with a follow up that I'll make a note of @TilakMaddy