place_pins and place_bumps steps usually mutually exclusive

[harrisonliew]

Definitely true in a flat design. In a hierarchical design, this is more complicated due to needing to place bumps + promoting pins (but hierarchical bumps are not properly supported anyway so it ends up being a hook).

Also, if there are no bumps assignments or pin mode is none (empty pin assignments list), these steps could be automatically removed (but still targetable for replacement?) so as to save unnecessary database writes (time saving for large chips).

[colinschmidt]

I like the idea of removing unneeded steps at the end. I imagine that could be applied across the board usefully.