Rollup merge of #107085 - tmiasko:custom-mir-operators, r=oli-obk

Custom MIR: Support binary and unary operations

Lower binary and unary operations directly to corresponding unchecked MIR
operations. Ultimately this might not be syntax we want, but it allows for
experimentation in the meantime.

r? ````@oli-obk```` ````@JakobDegen````

diff --cc compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
Simple merge