fix: compile HasLotusJson::snapshots for test target only

[hanabi1224]

Summary of changes

Originally part of https://github.com/ChainSafe/forest/pull/3964 , to drop a few Default derives for non test targets Using a separate PR to make both easier to review

Changes introduced in this pull request:

• compile HasLotusJson::snapshots for test target only

Reference issue to close (if applicable)

Closes

Other information and links

Change checklist

• [x] I have performed a self-review of my own code,
• [x] I have made corresponding changes to the documentation,
• [x] I have added tests that prove my fix is effective or that my feature works (if possible),
• [x] I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.