Add support for <ComponentLibrary> with package-local URIs

[sjbarag]

RBI's SceneGraph implementation supports a ComponentLibrary component, used to load components from a separately-packaged bundle of code. These can be loaded either via HTTP or via pkg:/-style local URIs (basically the same rules as <Poster/>) and add all .xml components to the list of createObject()-able components in the main channel. Those components must be prefixed by the namespace of the component library.

Useful Resources:

• A sample component library: https://github.com/rokudev/samples/blob/0b92a931ff5f5959e8d8f9361c9bfda012dbb143/utilities/ComponentLibrary.zip
• A sample channel using that component library: https://github.com/rokudev/samples/blob/0b92a931ff5f5959e8d8f9361c9bfda012dbb143/utilities/ComponentLibraryTestChannel.zip
• RBI documentation: https://developer.roku.com/docs/references/scenegraph/control-nodes/componentlibrary.md

[sjbarag]

I suspect this will require a small modification to ComponentProcessor::parseChildren, looking for child.name === "ComponentLibrary", then adding that URI to a list of component libraries that need to be handled. Each component library appears to be almost a fully-valid channel, so we'll need to go through the normal manifest + preprocessor + lexer + parser process for all .xml and .brs files in that .zip file.

The tricky bit is likely that <script/> tags in the component library are resolved relative to the manifest file of that component library, rather than process.cwd() like we currently assume.

To simplify things for now, let's reject /^https?:\/\/.*/ URIs, to avoid having to load remote resources during parse-time.