### What
When submitting a server action on a page that doesn't import the action
handler, a "Failed to find server action" error is thrown, even if
there's a valid handler for it elsewhere.
### Why
Workers for a particular server action ID are keyed by their page
entrypoints, and the client router invokes the current page when
triggering a server action, since it assumes it's available on the
current page. If an action is invoked after the router has moved away
from a page that can handle the action, then the action wouldn't run and
an error would be thrown in the server console.
### How
We try to find a valid worker to forward the action to, if one exists.
Otherwise it'll fallback to the usual error handling. This also adds a
header to opt out of rendering the flight tree, as if the action calls a
`revalidate` API, then it'll return a React tree corresponding with the
wrong page.
Fixes#61918Fixes#63915
Closes NEXT-2489
136979fedb