Support searching the marketplace for compatible notebook renderers

[connor4312]

Following microsoft/vscode#119899, there is a structure in the package.json which looks like:

{
	// ...
	"contributes": {
		"notebookRenderer": [
			{
				"id": "github-issues",
				"displayName": "Github Issues Notebook Renderer",
				"entrypoint": "./dist/renderer.js",
				"mimeTypes": [
					"x-application/github-issues"
				],
				"dependencies": [
					"gh-issue-kernel"
				]
			}
		]
	}
}

VS Code will know the mimeType and available kernelProvides list. We need to be able to issue a query which will return:

• Extensions that have the mimeType in its list of contributes.notebookOutputRenderer.mimeTypes list,
• excluding extensions who have a non-empty dependencies list which does not include anything in the kernelProvides list

In pseudo-code:

def search_extensions(mimeType, kernelProvides):
  for extension in extensions:
    if any(matches(c, mimeType, kernelProvides) for c in extension.contributes.notebookOutputRenderer):
      yield extension

def matches(contribution, mimeType, kernelProvides):
  if mimeType not in contribution.mimeTypes:
    return False
  
  if kernelDependency.dependencies is not None and len(kernelDependency.dependencies) > 0:
    if not any(d in kernelProvides for d in kernelDependency.dependencies):
      return False

  return True

We will then be able to show a helpful hint in VS Code if there are no renderers for a mimeType.