Treat _debugInfo as a wellknown property for sync request data access purposes (vercel#78942)

When we converted our request access APIs to async we supported sync
access to make the adoption easier. We do have a list of certain builtin
properties that exist on promises or are tested for in the course of
runtime operations that we say are not synchronously accessible however
and you must await the request data promise to access those if
necessary.

Recently it was discoverd that React will check the `_debugInfo`
property of thenables and other async data types in dev. This was being
reported as a warning when passing searchParams from RSC to client
world. By adding `_debugInfo` to the wellKnownProperties set we can
avoid this warning by also making it so you must await the promise to
access a true request value such as `?_debugInfo=...` in a search
string.

This change adds this property name to the well known set

Author: gnoff

packages/next/src/shared/lib/utils/reflect-utils.ts

@@ -40,6 +40,7 @@ export const wellKnownProperties = new Set([
 
   // React introspection
   'displayName',
+  '_debugInfo',
 
   // Common tested properties
   // fallthrough