Support major version upgrade via manifest and global upgrades via min version (#1372)

Support major version upgrade trigger via manifest. There is `off` `manual` and `full`. Manual is what you expect, and full will auto upgrade clusters below a certain threshold.

pkg/util/httpclient/httpclient.go

@@ -0,0 +1,11 @@
+package httpclient
+
+//go:generate mockgen -package mocks -destination=$PWD/mocks/$GOFILE -source=$GOFILE -build_flags=-mod=vendor
+
+import "net/http"
+
+// HTTPClient interface
+type HTTPClient interface {
+	Do(req *http.Request) (*http.Response, error)
+	Get(url string) (resp *http.Response, err error)
+}