Compile integer patterns to a switch instead of a nested if/else tree

[yorickpeterse]

Description

When matching against an Int, we currently compile the possible cases to what's essentially a nested if/else tree. However, LLVM's switch instruction works perfectly fine for integers that aren't contiguous. Compiling to a switch means LLVM might be able to better optimize the code based on the values we're matching against. This does require that on the MIR level we distinguish between exhaustive switches (as used for enum tags) and non-exhaustive switches.

Related work

No response