Expose read-latency and write-latency parameters of FIRRTL memories

[trmckay]

Contributor Checklist

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Type of Improvement

• Feature (or new API)

Desired Merge Strategy

• Squash: The PR will be squashed and merged (choose this if you have no preference).

Release Notes

• Support instantiation of SRAMs with read-latency and write-latency >= 1

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[linux-foundation-easycla]

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• ✅ login: trmckay / name: Trevor McKay (33161b3, 71c8249, 845be3b, d2c477b)

[trmckay]

Summary of the changes in this file:

• Add readLatency and writeLatency to the private impl functions
• For each public API
  • Set the default latency of 1
  • Add a copy of that method with latency parameters passed by the caller

If we expose additional parameters in the future, I think we can keep the minimal public APIs that were present before this PR, then add additional parameters to the new APIs added here.