Enable toggling off Cilium skip upgrades flag

**What would you like to be added**:

The EKS-A Cilium configuration offers a skip upgrades flag that turns the Embedded Cilium into an unmanaged CNI.

This ticket is to enable toggling off skip upgrades enabling users to revert to using the Embedded Cilium.

**Why is this needed**:

Start by locating the EKS-A Cilium configuration and the skip upgrades flag handling. Trace how enabling the flag makes Embedded Cilium unmanaged, then verify the reverse transition back to Embedded Cilium; the issue names no files or tests, so repository search is needed to identify the relevant coverage.

Written by the indexing model from the issue text.