MB-61890 - Introducing config for zap layer

[Thejas-bhat]

• Currently there isn't a concept of config at the zap layer and whatever storage level configurations present (at various points of index lifetime) are global variables. This forces all indexes' segments to use same values irrespective of how heavy indexes are.
• The PR introduces segmentConfig that can be used to pass index specific config values for the zap level. This would help in the future to perform any index specific tuning at the zap level.
• This involves extending the existing interface's Open and New APIs.
• The segmentConfig is something that's constructed by parsing the scorch.config and persisted in the index_meta.json file.