Compile time ABI encoding of constant values

[xermicus]

We should ABI encode compile time constant values at compile time. I had to work around this in #1449 for error data.

However it is not entirely clear yet how this will work. The following thoughts are extracted from a discussion in chat:

We thought of either adding a generic abi.encode instruction and resolving it later or simply adding markers to each instruction in the CFG so that we could identify that they belong to an encoding.

Depends on #1450