Save process environment variables in capture file

[bradgrantham-lunarg]

Add some kind of a block to capture that contains the process environment variables. E.g. "MESA_SHADER_CACHE_DIR" is an important variable for allowing Mesa to use the same cache for created graphics pipeline (compiled shaders) from run to run. If the environment was stored in the capture file, someone could take the output of gfxrecon-info or gfxrecon-convert and pull out environment variables of interest. This could be automated by a replayer script, maybe repurpose gfxrecon-replay-renamed.py to apply some heuristics and goop to set helpful environment variables, etc.

[bradgrantham-lunarg]

Is there an analog for Android? Android has environment variables and properties - is there a subset of that data that alters driver behavior that we would like to have restored in replay in #1575?