Refactor CNAB adapter to support multiple dependencies extensions

[carolynvs]

The cnab adapter needs to be updated to support generating either v1 or v2 of the dependencies extension for inclusion in bundle.json. The first step is to just refactor the adapter so that it can differentiate between which extension it is working with.

I've already started this in #2099 but we need to split this out into a PR that just implements this new pattern for v1, so that we can incrementally add this feature into Porter. When we finally implement advanced dependencies in a later PR, then we should be able to update the adapter with the v2 logic, and the adapter will correctly handle generating either v1 or v2 depending on which the bundle is using.

porter/pkg/cnab/config-adapter/adapter.go

Lines 414 to 428 in 58dc1e8

	func (c *ManifestConverter) generateDependencies() (interface{}, string, error) {
	if len(c.Manifest.Dependencies.Requires) == 0 {
	return nil, "", nil
	}
	// Check if they are using v1 of the dependencies spec
	if c.Manifest.Dependencies.Requires[0].Reference != "" {
	deps := c.generateDependenciesV1()
	return deps, cnab.DependenciesV1ExtensionKey, nil
	}
	// Ok we are using v2!
	deps, err := c.generateDependenciesV2()
	return deps, cnab.DependenciesV2ExtensionKey, err
	}

[carolynvs]

Implemented in #2246