Graph optimizations analysis info

[BramOtte]

Just a draft so people know this exists, its been quite a while since I have worked on this so I don't think its ready to merge.
It removes quite a few nodes and also improves runtime performance but significantly increases compile times.

[BramOtte]

I resolved the compile time issues with this PR now.
Previously for iris Mandelbrot it took 5 to 6 seconds to run the coalesce2 pass now its just ~350ms.
The ss_range_analysis pass also has a more reasonable compile time of 280ms which I think is still slower than master but it was closer to a whole second before and this pass is more effective than master.
I should be able to get this merge ready soon.

There are still a few things that keep this a draft:

• The coalesce2 pass uses unsafe to reduce copies and allocations, this brings its compile time down from 700ms to 350ms but if there is a safe way to achieve similar results I'd prefer that, if anyone has any ideas I would like to know.
• The coalesce2 pass currently does signal strength distance normalization, this could maybe be done in an earlier pass instead
• The ss_range_analysis pass could be optimized further it currently iterates over all the nodes repeatedly
• Ideally more than just iris is tested