Rolling buffer size enhancements, bug fix, and unit tests

[sirknightj]

Issue #, if available:
N/A

What was changed?

• Add proper size tracking (bug fix), which allows:
  • Able to check if it's at capacity and data will be overwritten.
  • DLOGI("Extract! Size: %d, index: %u, bounds: [%u - %u). Ago=%d", pRollingBuffer->size, index, pRollingBuffer->tailIndex, pRollingBuffer->headIndex, pRollingBuffer->headIndex - index); to check how many elements away from the head of the queue upon request.
• Handle integer overflow case when indexes wrap around UINT64_MAX.
• Add documentation for methods
• Add comments in the code
• Factored out the range check to a separate method.
• Added more unit tests to confirm behavior.
• Make rollingBufferGetSize and rollingBufferIsEmpty thread safe by adding locks.

Why was it changed?

• Make rolling buffer code more robust and more readable.

How was it changed?

• Refer to the code above.
• Note: The size needed to be its own variable because you can remove items from the buffer in an arbitrary order.

What testing was done for the changes?

• Run the new unit tests and they pass.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.