Merge the Cadence and Synopsys plugins into Hammer

[vighneshiyer]

I copied over the files from the Cadence and Synopsys plugin repos into hammer. There should be no functional changes. Running the e2e tests with the Cadence flow is still pending. Do we believe the Synopsys flow still works out-of-the-box?

[harrisonliew]

Let's not include Synopsys DC & ICC. These plugins are too old/not maintained (erase them from the git history too).

Otherwise, I don't see why directly copying them in should break anything.

[vighneshiyer]

I've squashed my commits and removed the DC/ICC plugins - let me know if there's anything else you'd like to fix. I still need to try the e2e tests.

[harrisonliew]

Looks good, pending e2e testing.

[harrisonliew]

Approving again, pending the other e2e test combos.

[vighneshiyer]

I've tested RTL->GDS in e2e using Cadence tools using sky130 on the A machines. There is an issue with post-syn and post-par simulation where the dff stdcell doesn't appear to update on the rising clock edge, but I suspect this is an issue with the PDK's verilog models and not related to this PR. We can merge this unless there's something else you'd like to check.

[harrisonliew]

All relevant issues from hammer-cadence-plugins and hammer-synopsys-plugins have been transferred over now.

[vighneshiyer]

Everything looks good to go - you can look over the diff one more time and if it looks good, we can merge.

[harrisonliew]

I had to cherry-pick this commit and update sky130 bwrc keys.