* Fix HTTP1 to HTTP2 migration while shutdown is in progress
### Motivation
Calling `HTTPClient.shutdown()` may never return if connections are still starting and one new established connection results in a state migration (i.e. from HTTP1 to HTTP2 or vice versa). We forgot to migrate the shutdown state. This could result in a large dealy until `.shutdown()` returns because we wait until connections are closed because of idle timeout. Worse, it could also never return if more requests are queued because the connections would not be idle and therefore not close itself.
###Changes
- Mirgrate shutdown state too
- add tests for this specific case
* simplify testMigrationFromHTTP1ToHTTP2WhileShuttingDown
* add http2 to http1 migration test
### Motivation
Our current swiftformat version does not support async/await. Since we want to add support for async/await we must update swiftformat or disable it. I tried my very best to keep the number of changes as small as possible. I assume we want to stick with the new 0.48.8 for some time.
### Changes
- Update swiftformat to 0.48.8
### Result
We can land async/await code.
David NadobaandGitHub
Fabian FettandGitHub