Replace `--ir` output with `--ir-optimized`

This is a different approach to the problem described in #13801.

`--ir` is the output straight from the codegen without any processing applied to it, while `--ir-optimized` is that code parsed again and then passed through `YulStack`, which may or may not apply optimizations to it, but will at the very least reformat it.

After #13972 `--ir` output is no longer the same as the unoptimized IR. The unoptimized IR has some minimal transformations applied to it to prevent "Stack too deep" errors. `--ir-optimized` is what the Yul->EVM actually runs on, and is the thing that should be given to the user.

My proposal here is to remove the current `--ir` output and then rename `--ir-optimized` to `--ir`. The same should be done in Standard JSON. The change is breaking.

Begin with the compiler's CLI handling of `--ir` and `--ir-optimized`, then trace the corresponding Standard JSON option. Confirm which path produces the YulStack-processed IR, and update both interfaces so the optimized output is exposed as `--ir`; done means the old behavior is removed consistently despite the breaking change.

Written by the indexing model from the issue text.