Revert "Increase cookies serialization priority value."

This reverts commit 22e10f647294e76ab78198e2ba6f2da3254b9637.
Style correction.
Correct priority of `session_end` hook.
Correct `findServerSocketConfig` function.

- Drop memoization.
- Move it out of scope of env contructor.
Move `ctx.url_to` to `ctx.helpers.url_to`.
Correct comment in navigate.js
Drop `req.pathname` and `req.fullUrl`.