12972 fetching changes should reload preview

[Jondyr]

Description

• Add onPullSuccess prop to VersionControlButton that is called when changes are successfully fetched.
• Call doReloadPreview when onPullSuccess is called from the page header

Related Issue(s)

• 12972

Verification

• [x] Your code builds clean without any errors or warnings
• [x] Manual testing done (required)
• [x] Relevant automated test added (if you find this hard, leave it and we'll help out)

Documentation

• [ ] User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.47%. Comparing base (34747d7) to head (0748a5b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #12979 +/- ## ======================================= Coverage 91.47% 91.47% ======================================= Files 1401 1401 Lines 19839 19843 +4 Branches 2397 2398 +1 ======================================= + Hits 18148 18152 +4 Misses 1427 1427 Partials 264 264 ```

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