feat(ui): postgres ha cluster (https://gitlab.com/postgres-ai/platform/-/issues/261)

Description

Related issue

https://gitlab.com/postgres-ai/platform/-/issues/261

Examples

Most of the components have been re-used from previous - DBLab SE installation.

Add route for clusters, along with new list item in the sidebar:

Postgres Cluster creation/installation modals:

Postgres Cluster creation page:

Postgres Cluster installation page:

Screens don't include simple install, docker and ansible steps.

Checklist

• MR description has been reviewed
• MR changes are functionally tested
• MR does NOT have API/CLI changes OR there are API/CLI changes and they have been reviewed & DOCS ARE ADJUSTED (reference doc, etc)
• MR does NOT have UI changes OR there are UI changes and they have been reviewed & UX IS REVIEWED