Use fast path helpers in BuildDetailsEntity

What does this MR do?

This MR swaps out the standard Rails path generators for some faster ones we built. I noticed while working with BuildArtifactEntity and BuildDetailsEntity at the same time that one used fast_* path generators and the other didn't. The behavior seems to be exactly the same, so why not use the faster ones?

Does this MR meet the acceptance criteria?

Conformity

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• Documentation (if required)
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done