## Changes
In order to support variable interpolation on fields that aren't a
string in the resource types, we need a separate representation of the
bundle configuration tree with the type equivalent of Go's `any`. But
instead of using `any` directly, we can do better and use a custom type
equivalent to `any` that captures additional metadata. In this PR, the
additional metadata is limited to the origin of the configuration value
(file, line number, and column).
The YAML in this commit uses the upstream YAML parser's `yaml.Node` type
to get access to location information. It reimplements the loader that
takes the `yaml.Node` structure and turns it into the configuration tree
we need.
Next steps after this PR:
* Implement configuration tree type checking (against a Go type)
* Implement configuration tree merging (to replace the current merge
functionality)
* Implement conversion to and from the bundle configuration struct
* Perform variable interpolation against this configuration tree (to
support variable interpolation for ints)
* (later) Implement a `jsonloader` that produces the same tree and
includes location information
## Tests
The tests in `yamlloader` perform an equality check on the untyped
output of loading a YAML file between the upstream YAML loader and this
loader. The YAML examples were generated by prompting ChatGPT for
examples that showcase anchors, primitive values, edge cases, etc.
Pieter Noordhuis