Add general encoding information for instructions

[Rot127]

Adds the encoding information for each instruction. @AngelDev06 did the first implementation in #2045

This PR adds a few changes:

• Rename ARM_MEM_FMT to something ISA or LLVM related. The current names are rather arbitrary and don't relate to the formatting as described in the ISA or LLVM definitions. Which makes it difficult to determine which encoding corresponds to which one in the ISA.

• Add an enum for ISA instruction formats for ARM (if possible). According to C2.1 (document DDI0553B.v)

• Generate for all other archs the encoding.

[Rot127]

@AngelDev06 Any objections against this (cff87a3) naming convention?

[AngelDev06]

@Rot127 None. I like it more than my version, which was a little rushed. It's better that you can now refer to the documentation rather than trying to make sense from comments.

[Rot127]

Closed due to: #2045 (comment)