* initial commit for SPRv2

* Add initial SPR cache handling

* update SPR handling

* Implement SPR handling in render

* Update tests, handle caching with serverless next
start, add TODOs, and update manifest generating

* Handle no prerender-manifest from not being used

* Fix url.parse error

* Apply suggestions from code review
Co-Authored-By: NJoe Haddad <joe.haddad@zeit.co>

* Replace set with constants in next-page-config

* simplify sprStatus.used

* Add error if getStaticProps is used with getInitialProps

* Remove stale TODO

* Update revalidate values in SPR cache for non-seeded routes

* Apply suggestions from code review

* Remove concurrency type

* Rename variable for clarity

* Add copying prerender files during export

* Add comment for clarity

* Fix exporting

* Update comment

* Add additional note

* Rename variable

* Update to not re-export SPR pages from build

* Hard navigate when fetching data fails

* Remove default extension

* Add brackets

* Add checking output files to prerender tests

* Adjust export move logic

* Clarify behavior of export aggregation

* Update variable names for clarity

* Update tests

* Add comment

* s/an oxymoron/contradictory/

* rename

* Extract error case

* Add tests for exporting SPR pages and update
/_next/data endpoint to end with .json

* Relocate variable

* Adjust route building

* Rename to unstable

* Rename unstable_getStaticParams

* Fix linting

* Only add this when a data request

* Update prerender data tests

* s/isServerless/isLikeServerless/

* Don't rely on query for `next start` in serverless mode

* Rename var

* Update renderedDuringBuild check

* Add test for dynamic param with bracket

* Fix serverless next start handling

* remove todo

* Adjust comment

* Update calculateRevalidate

* Remove cache logic from render.tsx

* Remove extra imports

* Move SPR cache logic to next-server

* Remove old isDynamic prop

* Add calling App getInitialProps for SPR pages

* Update revalidate logic

* Add isStale to SprCacheValue

* Update headers for SPR

* add awaiting pendingRevalidation

* Dont return null for revalidation render

* Adjust logic

* Be sure to remove coalesced render

* Fix data for serverless

* Create a method coalescing utility

* Remove TODO

* Extract send payload helper

* Wrap in-line

* Move around some code

* Add tests for de-duping and revalidating

* Update prerender manifest test