[MLIR] Reduce generated assembly printer compile time (NFC) (#225740)
Use fixed arrays for statically elided attributes and combine leading
spaces with literals. Move common operand printing out of generated call
sites and emit sliced operand getters to reduce optimizer work in large
printers.
For omp.target, optimized print IR drops from 3,893 to 2,667
instructions.
Assisted-by: Codex