feat(snapshot): ability to skip snapshot from custom serializer + attest example

[hi-ogawa]

Description

• closes Is it possible to add snapshots in type testing? #5857

From my quick research, there are currently two blockers for attest to be able to make use of Vitest snapshot system.

One is that, Vitest snapshot workflow normally expects a watch re-run, for example, for new inline snapshot or when updating failed snapshots. Attest relies on globalSetup to trigger analyze once, so this was the issue, but should be solved by #6803 and it looks good now.

Secondly, to support skipType mode (which is essential to allow running only normal tests without heavy typescript analysis), we'll probably need a concept of "skipped" snapshot check so that Vitest gracefully let invalid attest snapshots pass. This is what PR implements.

This approach assumes that attest is kept as 3rd party integration. If it'll end up as core feature, then there might be a way to special case attest usage like expectAttest().toMatchTypeSnapshot(), which then implement "skip mode" behavior there instead of doing the magic in serializer level, but I haven't investigate this direction yet.

tbd

• ideas for faster re-run?
• ideas for core integration e.g. custom attest alias like expectAttest?
• how to support attest in browser mode where fs is not available? (can we send precache result ahead and access it synchronously?)

todo

• fix windows

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