The language service incorrectly reports an error if it fails to find
NgModule metadata for a particular Component / Directive. In many cases,
the use case is legit, particularly in test.
This commit removes such diagnostic message and cleans up the interface
for `TypeScriptHost.getTemplateAst()`.
PR closes https://github.com/angular/vscode-ng-language-service/issues/463
PR Close#34113
The TemplateInfo type is an extension of AstResult, but it is not
necessary at all. Instead, improve the current interface for AstResult
by removing all optional fileds and include the TemplateSource in
AstResult instead.
PR Close#32250
