fix(@angular-devkit/build-angular): improve rebuild performance with loaders and prebundling

[clydin]

Processing overhead has been reduce during resolution when the fallback path is enabled for prebundling due to either prebundling exclusions or custom loader options being present. The resolution logic now follows the same behavior as the underlying bundler's external package option and avoids the need for an additional bundler resolution roundtrip. While the overhead of the plugin itself is still present, the execution cost is now greatly reduced. Further optimizations to conditionally include the plugin based on code analysis heuristics may be considered in the future.

Blocked on a separate refactoring to allow typescript path mapping entries to be added to the exclude list of the plugin.