As a first step towards TDS, add support for proto/JSON representations of the runtime virtual file
system and plumb this into bootstrap.
"numerator" and "denominator" are now reserved keywords and can't be used in runtime keys; this
simplifies parsing significantly. It is not expected that these are widely used, due to the
difficulty of ensuring atomicity if representing fractions, but this is technically a runtime API
breaking change.
Risk level: Medium (due to the reserved word changes).
Testing: Unit and server tests added.
Part of #6708
data-plane-api(CircleCI)
11cde5d7be