Deduplicate procmems by sha256 hash

[msm-cert]

This solves our "problems" with binaries that are submitted as copies of themselves, like b = open("x.exe").read(); b = b * 100.

bb4c7d48773b21c62885d0206c9414176c254e6104b4a0ffe730aa570b424948
21a479ce141d62b5920b3f76ece6d2b4a58c7f25afc8751e161a0fdf44a0197f
f5c9c598101a49a5c60f174fe7e7946c3f73c7c51b39ae5120560494d80db168

This is not an elegant fix for many reasons:

• We're defending about a specific class of malformed binaries, this is not really an obvious improvement (even though procmem deduplication makes sense in all cases, it's not expected to be useful often)
• Procmems with the same sha256 may behave differently because of subtle imagebase differences (I think i could prepare a toy examples where two procmems with the same .m hash behave differently because of imagebase.

It will hopefully stop us from OOMing, but it's not a critical fix.

[yankovs]

Hey! :)
Just stumbled upon this PR and wanted to share that recently I've been experimenting with dumps from emulation and came across (what I assume is) this behavior, same samples only difference being imagebase. I'll be happy to share hashes of such samples, if you need

[psrok1]

It looks like it's not really b*100 but binary were not correctly carved and m was pointing 100 times at the beginning of the buffer. I try to fix this in #122.