## Changes
This PR is the counterpart to #904. With this change, we are able to
convert a `config.Value` into a Go struct, make modifications to the Go
struct, and reflect those changes in a new `config.Value`.
This functionality allows us to incrementally introduce this
configuration representation to existing bundle mutators. Bundle
mutators expect a `*bundle.Bundle` argument and mutate its configuration
directly. These mutations are not reflected in the corresponding
`config.Value` (once introduced), which means we cannot use the
`config.Value` as source of truth until we update _all_ mutators. To
address this, we can run `convert.ToTyped` and `convert.FromTyped` at
the mutator boundary (from `bundle.Apply`) and capture changes made to
the Go struct. Then we can incrementally make mutators aware of the
`config.Value` configuration and have them mutate that structure
directly.
## Tests
New unit tests pass.
Manual spot checks against the bundle configuration type.
Pieter Noordhuis