Replace represent tuning options as a statically typed class (or hrecord) instead of as an untyped map

[shonfeder]

Factored out of #1177

The work on #1177 integrates all CLI options into the configuration management system. However, in the interest of working incrementally, the tuning map is currently left as a stryingly typed map. As a followup, we'd like to make this region of the configs well typed and amenable to static analysis.