## Changes
The new `dyn.Pattern` type represents a path pattern that can match one
or more paths in a configuration tree. Every `dyn.Path` can be converted
to a `dyn.Pattern` that matches only a single path.
To accommodate this change, the visit function needed to be modified to
take a `dyn.Pattern` suffix. Every component in the pattern implements
an interface to work with the visit function. This function can recurse
on the visit function for one or more elements of the value being
visited. For patterns derived from a `dyn.Path`, it will work as it did
before and select the matching element. For the new pattern components
(e.g. `dyn.AnyKey` or `dyn.AnyIndex`), it recurses on all the elements
in the container.
## Tests
Unit tests. Confirmed full coverage for the new code.
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