feat: forward completion and hover requests to html providers for inline templates
feat: forward completion and hover requests to html providers for inline templates

If we determine that we are inside an inline template in the client
middleware, forward completion and hover requests to the registered
providers for HTML content.

TODO: The @angular/language-service plugin should be updated to not give
_any_ DOM schema completions.
https://github.com/angular/angular/commit/45216ccc0d3cbb9182f879559c8e451e1bbe32b4
updated it to not provide those for external templates, but now we
should be able to remove them completely and allow the other providers
to give those completions.

fixes #561

angular/vscode-ng-language-service,angular/vscode-ng-language-service,angular/vscode-ng-language-service,angular/vscode-ng-language-service