Support esm externals in app router (#65041)
Support `esmExternals` working in app router
`esmExternals` was disabled for app router that most of the packages are
picking up the CJS bundles for externals. This PR enables to resolve the
ESM bundle for external packages.
We have two issues discovered while enabling the flag, any esm external
packages will fail in client page SSR and server action. We fixed them
by changing the below bundling logics:
* When a client page having a async dependency, we can await the page
during in rendering
* When a server action having a async dependency, we changed the server
action entry creation with webpack along with the server client entry
creation together, then webpack can handle the modules async propagation
properly.
Fixes #60756
Closes NEXT-2435
Closes NEXT-2472
Closes NEXT-3225
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Co-authored-by: Tobias Koppers <tobias.koppers@googlemail.com>
