Status color for closed alert; colors should be aligned with OpsGenie web UI

[marians]

The alerts list component (EntityOpsgenieAlertsCard) shows alerts with a colored dot that indicates status. Example:

Currently

• a closed alert is currently marked by a dot in color theme.palette.status.ok (green)
• an open and acknowledged alert has a dot in theme.palette.status.warning (yellow)
• an open alert that is not acknowledged gets theme.palette.status.error (red)

Source: https://github.com/K-Phoen/backstage-plugin-opsgenie/blob/v0.6.6/src/components/AlertsTable/StatusChip.tsx

To me personally, the combination of the color green for a closed alert is unexpected, as the green indicates more that something is "ready" or "active".

I suggest to align the colors with the OpsGenie web UI. Here they use:

• Red for an open, not acknowledged alert (#b23120 in dark, #d8351f in light)
• Light blue for an acknowledged alert (#a4adba in dark, #dfecfe in light)
• Transparent, gray outline only for a closed alert

OpsGenie web UI screenshots

Open (dark theme)

Open (light theme)

Acknowledged (dark theme)

Acknowledged (light theme)

Closed (dark theme)

Closed (light theme)