[EDR Workflows] Fix navigation not opening on Response Console view (#…

…195907)

The Response Console is a full-size overlay rather than a modal or page.
In the Serverless environment, we need to account for the space taken up
by the navigation on the left when it’s open as well as closed. To
accommodate this, we’ll subtract the navigation width (defined by the
`--euiCollapsibleNavOffset` variable) from the overlay width and apply
it as a left offset.

The `--euiCollapsibleNavOffset` variable is only declared for
Serverless, so these changes will not affect ESS, where navigation is
displayed as a popup rather than being integrated into the page layout.

With these changes:
Serverless:


https://github.com/user-attachments/assets/81955598-6ff1-4856-af08-ca5e9548a85c

ESS: 


https://github.com/user-attachments/assets/0bec1e24-58f6-45be-b846-feece89ecb63

x-pack/plugins/security_solution/public/management/components/page_overlay/page_overlay.tsx

@@ -27,9 +27,12 @@ const OverlayRootContainer = styled.div`
   top: var(--euiFixedHeadersOffset, 0);
   bottom: 0;
   right: 0;
+  left: var(--euiCollapsibleNavOffset, 0);
 
+  width: calc(100% - var(--euiCollapsibleNavOffset, 0));
   height: calc(100% - var(--euiFixedHeadersOffset, 0));
-  width: 100%;
+
+  border-left: 1px solid ${({ theme: { eui } }) => eui.euiColorLightestShade};
 
   z-index: ${({ theme: { eui } }) =>
     eui.euiZFlyout +