refactor: Deflake and Try package

- feat: add CI multiplier
- refactor: readability
- feat: custom Sleep function
- refactor(integration): use custom Sleep
- feat: show Try progress
- feat(try): try response with status code
- refactor(try): use a dedicate package.
- refactor(integration): Try everywhere
- feat(CI): pass CI env var to Integration Tests.
- refactor(acme): increase timeout.
- feat(acme): show Traefik logs
- refactor(integration): use `http.StatusXXX`
- refactor: remove Sleep

Makefile

@@ -7,7 +7,8 @@ TRAEFIK_ENVS := \
 	-e VERBOSE \
 	-e VERSION \
 	-e CODENAME \
-	-e TESTDIRS
+	-e TESTDIRS \
+	-e CI
 
 SRCS = $(shell git ls-files '*.go' | grep -v '^vendor/' | grep -v '^integration/vendor/')