add verilog customized name for generator

[joyliu37]

I made some changes to the verilog analysis passes and it work for me for the issue.
#941

[leonardt]

It seems like this is the code we should be trying to use: https://github.com/rdaly525/coreir/pull/1013/files#diff-1d13ccebd6fd308ba92fd6d7889462cc6b4a370afdbc5edb561dfe2ddab84781R1147-R1154 but because they metadata is lost when you save to JSON it's not working. Let me investigate the options there, perhaps we should save that metadata to be persistent across invocations. However, it's likely that you should also just be able to save the verilog file directly from the runtime which would avoid that issue.

[rdaly525]

@joyliu37 if you use serializeToFile(...) instead of saveToFile(...) All the metadata and dependencies will get saved in the one verilog file.