Piping the feedback to logs is disabled by default but can be enabled by patching the source for now. If reading from logs gets to be useful, we can move it behind a flag. In traces, enabled by default, pipeline cache hits and misses will be shown via counters. The time taken to create a pipeline variant is already covered by existing traces.
This patch also sets up infrastructure in the impeller::CapabilitiesVK to quickly enable optional device extensions.
Pipeline feedback will only be reported if the device supports `VK_EXT_pipeline_creation_feedback`.
Example of logs:
```
E/flutter ( 2011): >>>>>>
E/flutter ( 2011): Pipeline 'GaussianBlurAlphaDecal Pipeline' Time: 48.60ms Cache Hit: 0 Base Accel: 0 Thread: 481449901232
E/flutter ( 2011): Stage 1: Time: 12.91ms Cache Hit: 0 Base Accel: 0 Thread: 481449901232
E/flutter ( 2011): Stage 2: Time: 15.10ms Cache Hit: 0 Base Accel: 0 Thread: 481449901232
E/flutter ( 2011): <<<<<<
```
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