fix!: add correct location and snapshot fields in json reporter

[sheremet-va]

Description

JSON reporter incorrectly gets the location from the test error. Vitest 1.4.0 introduced --includeTaskLocation flag and we can now reliably take it from there (which actually follows jest behaviour).

This PR adds a missing snapshot property to the root of the json reporter.

The failureMessages now includes the full stack trace.

Related: #5350
Follow-up #5435

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