fix: add expect.soft support to toMatchSnapshot (#8673)

[iumehara]

Description

Resolves #8673

• toMatchSnapshot, matchSnapshot, toMatchFileSnapshot, toThrowErrorMatchingSnapshot can be used with expect.soft. These methods use the existing wrapAssertion function from expect utils.
• toMatchInlineSnapshot, toThrowErrorMatchingInlineSnapshot could not easily support expect.soft. These methods now throw an error if used with expect.soft

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[hi-ogawa]

Can you create tests in test/snapshots? test/core only allows single run, so it's probably hard to poke the edge cases here (e.g. creation scenario, update scenario, non-match scenario, etc)

[iumehara]

@hi-ogawa , can you clarify what I should test in test/snapshots?
It seems like the edge cases (ie. creation, update) will ALWAYS pass. Is that not the case? If so, it'll never exercise the new behavior, which is a side-effect of a failing snapshot test.
Is it that you would like test coverage for assurance that expet.soft has no unexpected side-effects in the success scenario? Or is there something else that I am missing?

[hi-ogawa]

Sorry, my suggestion was a bit vague and I don't have concrete suggestion. Some ideas are:

• it looks like currently tests are relying on manipulating snapshotState and result.state from tests itself to simulate certain scenarios. this feels a bit brittle and ideally each scenario should be tested in a more realistic way like users would actually write tests.
• for example, test/snapshots/test/skip-test.test.ts runs same test suites multiple times with different config/snapshot to test various scenarios.

[hi-ogawa]

For example, one "brittleness" is that current tests would break with force update pnpm test snapshot-test -u. So this type of tests should belong to elsewhere in general.

[iumehara]

@hi-ogawa , thanks for your detailed input.
I moved the testing to the snapshots directory like you suggested.
I defined an AlwaysFailingSnapshotSerializer in order to test the failure tracking behavior across the different scenarios.
Please let me know what you think.