This commit adds an API to `NgCompiler`, a method called
`getComponentsWithTemplateFile`. Given a filesystem path to an external
template file, it retrieves a `Set` (actually a `ReadonlySet`) of component
declarations which are using this template. In most cases, this will only be
a single component.
This information is easily determined by the compiler during analysis, but
is hard for a lot of Angular tooling (e.g. the language service) to infer
independently. Therefore, it makes sense to expose this as a compiler API.
PR Close#39002
8f11b516f8