Add several new entrypoints to `Dhall` module

[Gabriella439]

This adds the following four new high-level entrypoints:

• interpretExpr
• interpretExprWithSettings
• fromExpr
• fromExprWithSettings

… as well as several new utilities for running each phase one at a time, respecting InputSettings:

• parseWithSettings
• resolveWithSettings
• typecheckWithSettings
• expectWithSettings
• normalizeWithSettings

This also refactors the other utilities to use those new phase-based settings.

The motivation behind this change is to make it easier for people to work with raw Exprs, so that people don't need to craft strings when trying to assemble ASTs to interpret like in this issue:

https://stackoverflow.com/questions/77037023/is-there-an-elegant-way-to-override-dhall-records-in-haskell

[mmhat]

@Gabriella439 I think it was nice if there was also a function checkWithSettings :: InputSettings -> Expr Src Void -> Expr Src Void -> m () that is something between expectWithSettings and typecheckWithSettings: A function that typechecks an input value against a type provided as an Expr. That way one does not need to construct an incomplete Decoder with extract = undefined.