Save batch data to file after batch evaluation

[yngve-sk]

Issue
Resolves #10235

Approach
Write results after each batch evaluation, then do a final overwrite at the end. Final overwrite would not have to happen if it weren't for parsing of the dakota merit values.

(Screenshot of new behavior in GUI if applicable)

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'just rapid-tests')

When applicable

• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Create Backport PR to latest release

[codspeed-hq]

CodSpeed Performance Report

Merging #10243 will not alter performance

_{Comparing yngve-sk:25.03.07.save-batchdata-instantly (a8584a5) with main (657656b)}

Summary

✅ 25 untouched benchmarks

[frode-aarstad]

Is it possible to add a regression test for this?

[yngve-sk]

Is it possible to add a regression test for this?

Added a regression test