Service-configuration-lib

What's Changed
* MLCOMPUTE-967 | Spark config calculation should result in failure if srv-configs can't be read by CaptainSame in https://github.com/Yelp/service_configuration_lib/pull/142


**Full Changelog**: https://github.com/Yelp/service_configuration_lib/compare/v2.18.14...v2.18.15

What's Changed
* MLCOMPUTE-1155 | fix cost factor default while reading spark costs from srv configs by CaptainSame in https://github.com/Yelp/service_configuration_lib/pull/138
* MLCOMPUTE-1160 | consolidate tron and paasta logic to service config lib by CaptainSame in https://github.com/Yelp/service_configuration_lib/pull/139


**Full Changelog**: https://github.com/Yelp/service_configuration_lib/compare/v2.18.11...v2.18.12