[WIP] Implement new "standalone" snapshots.

[seansfkelley]

Summary

#6383 (comment)

(More detail coming later.)

Test plan

TODO

• How to name the standalone directory? Currently the PR just tacks .standalone onto the end.
  • Originally I wanted the standalone name to be the snapshot name minus .snap, but this meshes awkwardly with the resolveSnapshotPath API.
• Existing snapshots are versioned. An explicit goal of standalone snapshots is that they don't have any of the Jest export/comment metadata, since they should be legal files in whatever language they're serialized as. Should these be versioned?
• It is an explicit goal that users can provide an arbitrary extension that comes last on the standalone snapshot's file name so that other tools can infer the proper file type based on the file name. How does Jest know which files in the standalone directory are snapshots, and which are not?
  • Currently, the heuristic just looks for .snap in the filename. This seems too lax.
  • Even if users don't intend to put other files in these directories, some of their actions can cause files to appear there (.DS_Store comes to mind on macOS).
• Bikeshed: I renamed the old snapshots (internally) to "grouped" and the new ones are called "standalone".

[linux-foundation-easycla]

• ❌ - login: @seansfkelley / name: Sean Kelley . The commit (ffaaa2d) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[netlify]

✅ Deploy Preview for jestjs ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	ffaaa2d
🔍 Latest deploy log	https://app.netlify.com/sites/jestjs/deploys/64c9947e82c869000756b719
😎 Deploy Preview	https://deploy-preview-14380--jestjs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[github-actions]

This PR is stale because it has been open 1 year with no activity. Remove stale label or comment or this will be closed in 30 days.

[github-actions]

This PR was closed because it has been stalled for 30 days with no activity. Please open a new PR if the issue is still relevant, linking to this one.

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
Please note this issue tracker is not a help forum. We recommend using StackOverflow or our discord channel for questions.