Add text parsers to STGen parser examples

[mikelui]

This issue tracks progress of copying the parser from the SynchroTrace replayer to the STGen example parsers.

Currently example parsers exist for the capnproto format traces.

This is because it's a less common format, so I figured it would be more approachable for peers to use if they could toy around with an already capable parser.

However, the SynchroTrace replayer was originally designed to parse the text format.
In recent changes, the text parser for the replayer also changed. It would be beneficial to fully decouple that text parser for easier testing and integration.