Implement read-write memory accessors for SyncReadMem (backport #3190)

[mergify]

This is an automatic backport of pull request #3190 done by Mergify.

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Original PR Body

Implements SyncReadMem.readWrite(address, writeData, enabled, isWrite) as a way to explicitly instantiate a readwrite port for a memory. This addresses the problem of unintentionally creating multiple read or write ports through multiple calls of SyncReadMem.read() and/or SyncReadMem.write(). Additionally, implements clocked and masked versions of readWrite for parity with the existing read and write functions.

Compare:

val myMem = SyncReadMem(100, UInt(32.W))
val readValue = myMem.read(someAddress)
when (timeToWrite)
  myMem.write(someAddress, valueToWrite)
when (timeToWrite) 
  myMem.write(someAddress, valueToWrite)

which instantiates a 1R2W memory, as opposed to

val myMem = SyncReadMem(100, UInt(32.W))
val rwPort = myMem.readWrite(someAddress, writeData, portEnabled, timeToWrite)

val readValue = rwPort
when (timeToWrite)
  writeData = valueToWrite
when (timeToWrite)
  writeData = differentValueToWrite

which instantiates a 1RW memory.

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)

Desired Merge Strategy

squash and merge

Release Notes

SyncReadMem.readWrite(address, writeData, enabled, isWrite) explicitly generates a read-write port that supports both read and write access to the memory.

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: 3.5.x or 3.6.x depending on impact, API modification or big change: 5.0.0)?
• 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.