edge: use JSON parse instead of inlining the manifests objects (#50960)
Manifests tend to be really big and our strategy is to inline them in the edge function script itself and we're hitting some constraints this way.
This PR switches this behaviour via inlining the script and creating a JS object at runtime instead, with the hope that the parsing time will be faster as JSON.parse is very well optimised in V8.
The end goal ofc is to have smaller manifests but this should be a good stopgap.
link NEXT-1273