refactor(date): Use Jest fake timers

[zharinov]

Changes

Sometimes CI randomly fails like this:

util/date › getElapsedMilliseconds › returns elapsed time in milliseconds

    expect(received).toBe(expected) // Object.is equality

    Expected: 9469618351
    Received: 9469618352

      44 |     it('returns elapsed time in milliseconds', () => {
      45 |       const elapsedMs = new Date().getTime() - new Date(Jan1).getTime();
    > 46 |       expect(getElapsedMs(Jan1.toISOString())).toBe(elapsedMs);
         |                                                ^
      47 |     });
      48 |   });
      49 | });

      at Object.<anonymous> (lib/util/date.spec.ts:46:48)

This PR should fix it.

Context

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[viceice]

can be removed, as each test file is isolated

[renovate-release]

🎉 This PR is included in version 35.55.1 🎉

The release is available on:

• GitHub release
• 35.55.1

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