Draft: Sunroof based eDSL for JS Backend

Towards fixing: #22736

Not Draft when:

• StableName is removed (and perhaps all of data-reify)
• Operational is removed
• Threading is removed
• add named, typed variables to JSI
• generated JS is readable
• generated JS is correct
• We've demonstrated that we can begin to rewrite the RTS with the eDSL (i.e., the testsuite passes with a mix of GHCJS DSL and this one)
• Each module has docs that explain the module
• JS.Monad explains the design and architecture of the eDSL