feat(@angular-devkit/build-angular): export `@angular/platform-server` symbols in server bundle

[alan-agius4]

This commit adds an internal file to export needed symbols from @angular/platform-server when building a server bundle. This is needed. This is needed so that DI tokens can be referenced and set at runtime outside of the bundle.

Also, it adds a migration to remove these exports from the users files as otherwise an export collision would occur due to the same symbol being exported multiple times.

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