[WIP] Feature/sql exec cost estimate

[Yaiba]

This pr implements simple exec cost estimation feature, by doing following steps:

1. convert AST to logical plan
2. do simple logical plan optimization
3. convert logical plan to a virtual plan based on statics
4. calculate a cost from a virtual plan

[jchappelow]

Thanks for the parse updates!

[Yaiba]

close in favor of #913 and #929