feat: git migrate modal

[dennisvankekem]

Figma: 

https://www.figma.com/design/Y5Yuc40oWpPfQJBFLD25Bp/Configure-Git-Pop-Up-Modal?node-id=0-1&p=f&t=68Aiyz87HLp84Vto-0

console:

#772

api:

linode/apl-api#976

Considerations

• I have tested the changes in both light and dark mode.
• I have considered the need for new unit tests.
• I have tested the changes on a cluster.
• I have included relevant documentation updates.
• I have an approved Figma design or have reflected my changes in Figma
• I have verified that the UI/UX is consistent in major browsers (e.g., Chrome, Firefox, Safari, Edge).
• I have tested the changes for responsiveness in different screen resolutions.
• I have tested expected error states and verified that the user is presented with informative error messages.
• I have tested the feature with unusual or extreme inputs (e.g., very long strings, empty states, clicking a button multiple times quickly).

[ElderMatt]

I can see an error behind the modal when a repository does not exist.

[ElderMatt]

The Git button in platform settings does nothing if isPreInstalled flag is not true.