wpif code transform

[agle]

Implement the information flow logic described in Winter, Coughlin, Smith 2021 at CSF and for BASIL in https://github.com/UQ-PAC/BASIL/blob/main/docs/iflogic-encoding.pdf

• It should lower the Gamma/Classification intrinsics to concrete ghost state and function applications
• It requires slight generalisation from the literature to fully cover our IR structures. Notably we specify classifications of memory/maps as functions from keys to booleans. We may want to simplify some type system stuff to make that reasoning easier; or have some integration with the memory lowering pass. We do want cell-precise reasoning about arrays and records.
• When unspecified assume a default gamma.

Break the feature up into the following layers:

• value independent information flow Value-independent information-flow transform #207
• value-dependent information flow
• value dependent information flow with rely guarantee
• value dependent infoflow with R/G and function rule