The `DirectoryWalkerEntryPointFinder` has to traverse the
entire node_modules library everytime it executes in order to
identify the entry-points that need to be processed. This is
very time consuming (several seconds for big projects on
Windows).
This commit changes the `DirectoryWalkerEntryPointFinder` to
use the `EntryPointManifest` to store the paths to entry-points
that were found when doing this initial node_modules traversal
in a file to be reused for subsequent calls.
This dramatically speeds up ngcc processing when it has been run once
already.
PR Close#35931
ec9f4d5bc6