This change enables dts bundling for the following packages and their secondary entry points:
- @angular/animations
- @angular/elements
- @angular/http
- @angular/platform-browser
- @angular/platform-browser-dynamic
- @angular/platform-server
- @angular/platform-webworker
- @angular/platform-webworker-dynamic
- @angular/servce-worker
Dts bundling happens in `ng_module` bazel definition, hence packages such as `@angular/compiler`, `@angular/compiler-cli` and `@angular/langauge service` cannot be flattened as they use `ts_library`.
`@angular/core`, `@angular/common`, `@angular/upgrade` and `@angular/forms` will be done seperatly as it requires some changes either to their source or specs.
PR Close#28726