fix(jest-circus): preserve Error.cause in JSON failureMessages (#15949)

[xamgore]

Preserve Error.cause in JSON failureMessages for both jest-circus and jest-jasmine2.

Summary

Fixes #15949.

The CLI already showed error causes, but JSON results could drop them in assertionResults[*].failureMessages.

The gap was in runner-level serialization:

• jest-circus built failure messages from error.stack / error.message
• jest-jasmine2 reporter did the same for failedExpectations

Node stacks do not include the full cause chain, so nested causes were missing in JSON output.

This PR updates both runners to serialize causes recursively with a [cause]: ... marker, including:

• nested Error causes
• string causes
• circular cause protection

Changes:

• packages/jest-circus/src/utils.ts
• packages/jest-jasmine2/src/reporter.ts

Tests:

• e2e JSON assertion in e2e/__tests__/failures.test.ts checks both:
  • [cause]: Error: error during g
  • [cause]: here is the cause
• added jasmine2 unit coverage in packages/jest-jasmine2/src/__tests__/reporter.test.ts

Test plan

Ran:

• yarn eslint e2e/__tests__/failures.test.ts packages/jest-circus/src/utils.ts packages/jest-jasmine2/src/reporter.ts packages/jest-jasmine2/src/__tests__/reporter.test.ts
• yarn jest e2e/__tests__/failures.test.ts -t "includes error causes in JSON failureMessages" --runInBand
• JEST_JASMINE=1 yarn jest e2e/__tests__/failures.test.ts -t "includes error causes in JSON failureMessages" --runInBand
• yarn jest packages/jest-circus/src/__tests__/utils.test.ts --runInBand
• yarn jest packages/jest-jasmine2/src/__tests__/reporter.test.ts --runInBand

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• ✅ login: xamgore / name: Igor Strebz (3b9ded1, a6ec61c, d4c69bb)

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commit: d075c34