Preview of improved Functions http scaling behavior #90

We have made improvements to the http scaling, which greatly improves those scenarios. At this point, a Preview of the behavior can be tried by setting an App Setting on your app: WEBSITE_HTTPSCALEV2_ENABLED=1.

Notes:

• Despite the flag having 'v2' in its name, this works with either the v1 or v2 runtime
• The flag is temporary. When the changes are fully released, they will be on by default for everyone
• There will also be further improvements when it is released. But the flag as it exists today already gives nice improvements over the current scaling.