Tracks Decoding Context for Instructions in Worklist

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This PR gets anvill building against remill https://github.com/lifting-bits/remill/pull/617 and should encompass most of the anvill side changes to support mixed mode. The last thing to work out here is how we want to specify building the initial context per function ie. for a thumb labeled function we need an initial context with TM set to 1. One possibility is to have a context assignment list in the spec for functions