Update Cluster Settings Flow in Portal UI

[SergK]

Is your feature request related to a problem? Please describe.
The current cluster settings flow in the Portal UI, which includes a modal window on first login and a separate cluster settings page, is not integrated well with the overall user experience. This setup makes the process cumbersome and disjointed for users.

Describe the solution you'd like
We propose to remove the modal window and the separate cluster settings page. Instead, we plan to integrate notification logic directly into the headlamp core repository and repurpose the account setting modal window to allow users to define their 'default namespace'. This will streamline the user experience by consolidating cluster settings into a single, more intuitive interface.

Describe alternatives you've considered
N/A - The proposed solution is the most effective way to integrate cluster settings into the Portal UI without disrupting the user experience.

Additional context
The update aims to improve the integration of cluster settings within our system, making it more user-friendly and efficient. It's crucial to ensure that the transition to the new flow is seamless and does not negatively affect other functionalities.

Acceptance Criteria:

1. The modal window that appears on the first login is removed.
2. The separate page for cluster settings is removed.
3. Notification logic is successfully moved to the headlamp core repository.
4. The account setting modal window is repurposed to allow users to define their 'default namespace'.
5. Test the updated flow to ensure that the 'default namespace' can be set and retrieved accurately.
6. Ensure that the integration does not affect other functionalities negatively.

Implementation Plan:

1. Analyze the current implementation of the cluster settings flow.
2. Remove the modal window and the separate page for cluster settings.
3. Migrate notification logic to the headlamp core repository.
4. Update the account setting modal window to include 'default namespace' configuration.
5. Conduct thorough testing on the updated flow.
6. Deploy the changes to a staging environment for further testing before releasing.