Issue #922: Improve refresh button positioning

[kush2439p]

Summary

• keep the Checkstyle configuration refresh button next to the rebuild preference
• prevent the button from consuming spare horizontal space and being pushed to the edge of the preferences page

Root cause

The refresh button's grid data grabbed all excess horizontal space and aligned the button at the far end of that expanded cell. On laptop-sized displays, this could leave the button partially clipped and contribute to horizontal scrolling.

User impact

The refresh action remains fully visible beside the rebuild dropdown at narrower resolutions, including the 1536 x 864 scenario reported in #922.

Validation

• git diff --check
• attempted ./mvnw.cmd -pl net.sf.eclipsecs.ui -am verify; dependency download completed, but Tycho stalled while resolving the Eclipse target platform in the sandbox

Fixes #922

[kush2439p]

Hi maintainers, following up on this PR since it has been open for several weeks without review. The layout fix is ready for review, and I am happy to adjust it or provide any additional validation you need. Thank you.

[Calixte]

It was not reviewed because it was in Draft mode and I assumed you were still testing it.
Do you have a screenshot of the change?