Creates the foreign view mechanism to support standard ViewContainerRef
using a dedicated ɵForeignViewRef implementation. Updates tests to use
public APIs (vcr.detach and vcr.insert), asserts on total innerHTML, and
exports ɵForeignViewRef privately from core.

- Added the ForeignComponent type in @angular/core.
- Added Component.foreignImports for importing ForeignComponents.
- Updated the compiler to handle ForeignComponent in template dependencies.
- Updated ngtsc to extract foreignImports from standalone components.

Note the compiler doesn't do anything yet with these imports.

… for foreign components

We extract the identifier name from the `foreignImports` expression in
`ComponentDecoratorHandler` and use a `SelectorlessMatcher` to match element
tags against these names during template binding in `R3TargetBinder`. If an
element matches both a regular Angular directive and a foreign component, a
conflict error is thrown.

In addition, we implement strict template semantic validation for these matched
foreign components within `TemplateSemanticsChecker`. Elements matched as foreign
components only support static attributes and property bindings. Any event
bindings, template references, or non-property input bindings (e.g. class, style,
or attribute bindings) trigger a semantic error diagnostic.

Finally, we skip standard DOM schema checks for foreign components to prevent spurious
validation errors since foreign components are not defined in standard HTML schemas.