wireprotov2server: port to emitrevisions()
We now have a proper storage API to request data on multiple
revisions. We can drop it into wire protocol version 2 with
minimal effort.
The new API handles pretty much everything we were doing manually to
build up the delta request. So we were able to delete a lot of code.
As a bonus, wireprotov2 code is no longer accessing some low-level
storage APIs. This includes the assumption that a node has an
associated numeric revision number! This should make it drastically
simpler to implement a server that doesn't have the concept of
revision numbers.
Differential Revision: https://phab.mercurial-scm.org/D4724
tests: use more complex file storage test
The previous test was attempting to to test delta storage behavior.
It didn't do a very good job at it because there was a good chance
a delta wasn't being used in storage.
Let's switch the test to yield a delta in storage so an upcoming
change to delegate delta logic to storage has the desired effect.
Differential Revision: https://phab.mercurial-scm.org/D4723