Resolve "Provide a migration strategy to transition from Operator Istio to Helm Istio"

Package Merge Request

Provides documentation for cluster admins to perform an Operator to Operatorless migration in this doc:

• /docs/guides/using-bigbang/migrating-istio-for-bb3.0.md

Also, this fills in two missing comment lines in BB values.

Package Changes

N/A

Package MR

N/A

For Issue

Closes #2283 (closed)

Upgrade Notices

N/A

chart/values.yaml

@@ -190,7 +190,9 @@ istioCore:
 
 istioGateway:
   status: "alpha"
+  # -- Toggle deployment of Istio Gateway(s)  
   enabled: false
+  # -- Choose source type of "git" or "helmRepo"
   sourceType: "git"
   git:
     repo: https://repo1.dso.mil/big-bang/product/packages/istio-gateway.git