[svsim] Expose further verilator options for trace file name and simulation speed optimization

[kammoh]

• Changed TraceStyle.Vcd to include a trace file name
• Added OptimizationStyle.OptimizeForSimulationSpeed and associated verilator flags to achieve simulation speed.
  • "--x-assign ast" and "--x-initial fast" flags should not really affect behaviour of most Chisel/CIRCT generated code and seem to give some performance boost, but it's open for feedback.
• added "-j 0" flag to verilator arguments to enable arallelism for uses all available CPU cores for verilate and build jobs
• added a "ShutdownHook" to kill the simulation process in case of Ctrl+C etc. Tested on macOS only, but seems to be working.

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• Did you add at least one test demonstrating the PR?
• Did you delete any extraneous printlns/debugging code?
• Did you specify the type of improvement?
• Did you add appropriate documentation in docs/src?
• Did you request a desired merge strategy?
• Did you add text to be included in the Release Notes for this change?

Type of Improvement

• Feature (or new API)
• API modification

Desired Merge Strategy

• Squash: The PR will be squashed and merged (choose this if you have no preference).
• Rebase: You will rebase the PR onto master and it will be merged with a merge commit.

Release Notes

Reviewer Checklist (only modified by reviewer)

• Did you add the appropriate labels? (Select the most appropriate one based on the "Type of Improvement")
• Did you mark the proper milestone (Bug fix: 3.6.x, 5.x, or 6.x depending on impact, API modification or big change: 7.0)?
• Did you review?
• Did you check whether all relevant Contributor checkboxes have been checked?
• Did you do one of the following when ready to merge:
  • Squash: You/ the contributor Enable auto-merge (squash), clean up the commit message, and label with Please Merge.
  • Merge: Ensure that contributor has cleaned up their commit history, then merge with Create a merge commit.

[linux-foundation-easycla]

• ✅login: kammoh / (40b4209)

The committers listed above are authorized under a signed CLA.

[jackkoenig]

LGTM, thanks @kammoh!