Increments to layer_gpu_timeline

[solidpixel]

The following changes were out of scope for the first PR and would make good follow-on increments.

• Add CPU submit time to the layer metadata so we can show the submit-to-execute latency, and sort by submit time not just execution start time. This will be another case where multi-submit command buffers won't work without us wrapping command buffers with a unique submit_id label.
• Track VkImage resources for transfer workload sizing.
• Track VkBuffer resources for transfer workload sizing.
• Replace JSON with a simple binary packet format, or protobuf, to avoid the memory allocation churn.
• Support arbitrary user string metadata in the protocol to allow custom layers to be used with Streamline visualization.
• Capture indirect parameter buffers.
• Improve the prototype Python host services server to make it production ready.
• Capture attachment compression status.
• Identify render pass rendering to swapchain attachment.

Completed:

• Change label metadata to a JSON list to preserve the stack, rather than merging with | separators, as we don't escape the separator if the label contained it. (Done in Timeline JSON preserves stack #40)
• Improve helper scripts to support gathering logcat files (Done in Android helper script enhancements #41)
• Improve helper scripts to support gathering Perfetto files (Done in Android helper script enhancements #41)
• Improve helper scripts to support gathering metadata files (Done in Android helper script enhancements #41)