fix(1632): erase const enums after inlining

[a-tarasyuk]

Fixes #1632

[jakebailey]

So, this seems probably right but will defer to @weswigham 😄

[a-tarasyuk]

@jakebailey ok, thanks

[weswigham]

I was unsure if we wanted this behavior back and didn't just wanna make const enums always preserved, since that's what we were doing before we re-added inlining, but I suppose since vscode reported it, they'd like the runtime source elision behavior back, too. Tbh, preserveConstEnums should at least be the default nowadays, but that's a change for another PR.

We also need to elide namespace declarations containing exclusively const enums and/or types (preserveConstEnums dependent) for the same reasons you'd want the const enums elided. See the missing shouldEmitModuleDeclaration call from the original ts.ts source. ast.GetModuleInstanceState is already ported, so it shouldn't be too bad.

[weswigham]

Pretty good - some last comments on comment preservation, since we're working with NotEmittedStatements which explicitly exist to copy those.