[json] jsonValidation fileMatch is confusing when used with URIs

- VSCode Version: 1.30.2 - OS Version: macOS 10.14.3 Steps to Reproduce: 1. Create an extension that [registers a text document content provider](https://code.visualstudio.com/api/references/vscode-api#2290) for a custom scheme, say `custom`. Implement the provider to return a json object as text. 2. Declare a jsonValidation in package.json with a `fileMatch` of `custom://*.todo`. 3. [Open](https://code.visualstudio.com/api/references/vscode-api#2246) a text document for a uri under that custom scheme with path ending in something.todo, and also a defined query or fragment [1], then [set text document language](https://code.visualstudio.com/api/references/vscode-api#2319) to 'json', and [show it](https://code.visualstudio.com/api/references/vscode-api#2074). 4. Expect the json schema validation to occur on the virtual file. 5. Note that it does not. It appears the `fileMatch` matches on the entire uri, including the query and the fragment! You can verify this by changing the `fileMatch` to `custom://*.todo?*` It should probably only match on the path. [1] e.g. `custom:/path/to/something.todo?foo`