Added clusters overview grid for Kafka Connect

[AlexisD02]

What changes did you make?

This pull request introduces a new feature to Kafka UI that provides an overview of Kafka Connect clusters. This enhancement allows users to see detailed information about each Kafka Connect cluster, including:

• Cluster name
• Cluster version
• Number of connectors (with a breakdown of running connectors vs. total connectors)
• Number of tasks (with a breakdown of running tasks vs. total tasks)

Changes Include:

• Added a new grid view under the "Kafka Connect" menu in the sidebar to display Kafka Connect clusters with the specified columns.
• Implemented a switcher button to toggle between the "Connectors" and "Clusters" grids. The "Connectors" grid is displayed by default when "Kafka Connect" is selected from the sidebar.
• Updated the interface to include the number of clusters along with the number of connectors, failed connectors, and failed tasks.

Is there anything you'd like reviewers to focus on?

Please review the following aspects:

• Ensure the Kafka Connect clusters grid is correctly displaying all required columns and data.

Fixes issue: #445

[Haarolean]

Hi, thanks for your PRs. I think we'll get back to them once we're done with our current milestone, to avoid extending the scope of one :)