Fix #6551 Use action getLatestApplicableVersionAndRev only when needed

[mpilgrem]

• Any changes that could be relevant to users have been recorded in ChangeLog.md.
• The documentation has been updated, if necessary

Please also shortly describe how you tested your change. Bonus points for added tests! Relying on CI.

[wraithm]

@mpilgrem I confirmed that this gives a ~7-8 s no-op build time on our repo! This does indeed fix a solid chunk of #6551. Thank you! :) There might be something else that is accounting for that additional 7-8 s that stack-2.7.5 isn't doing (which usually takes <2 s).