Bumps dependencies to get rid old version of ring (<0.17)

[sr-gi]

rcgen was using version 0.8 which used a ring version that didn't support ppc64le arch. Support for it was recently added in ring=0.17.0 and supported by rcgen in 0.12

tonic also had a chain dependency to ring, so it needed updating (and therefore also prost)

Close #243

[sr-gi]

Looks like we may need to pause this for a bit more. tonic also has a dependency chain to ring

[sr-gi]

Made some progress updating tonic. We still have a last dependency to an old ring version from using x509-parser. However, looks like they are about to cut a release bumping their deps.

https://github.com/rustls/rcgen/issues/236