Create istio-gateway Package Repo

In support of https://repo1.dso.mil/platform-one/big-bang/bigbang/-/issues/587, a separate package is required to manage Istio gateways resources. Currently, Gateways are managed by the istio-controlplane package. This causes Gateways to be recreated when canary upgrading. Separating Gateway management from istio-copntrolplane allows zero downtime of VirtualServices during a canary upgrade.

xref current istio-gateway GitHub repo: https://github.com/danehans/istio-gateway

cc: @michaelmcleroy @stas

Sandbox repo created: https://repo1.dso.mil/platform-one/big-bang/apps/sandbox/istio-gateways

@michaelmcleroy thanks for creating the repo. Should I close this issue now?

closed