Extresist command does not work correctly on hierarchy

[RTimothyEdwards]

This is a placeholder for the known issue that "extresist" often produces incorrect results on a hierarchical design. Currently the recommendation is to always flatten a circuit before running "extresist", but the problem needs to be investigated and fixed.

Also, need to remove the dependence on the ".sim" format file as part of "extresist" and make it dependent only on the ".ext" file.

[Li-Yueting]

Hi Tim, would you mind sharing the current Tcl RC extraction code that running in magic for analog design's post-layout pex?