fix: prevent birpc timeouts when Math.random mock is not restored

[AriPerkkio]

• Fixes Timeout Error when Calling "onAfterSuiteRun" in "birpc" Module during Test Run #3457 (reply in thread)
• Related to Mocking Math.random and not restoring makes vitest hang up when coverage is enabled #903
• Related to Mocking Math.random Causes Random birpc Timeouts #2230
• birpc changes fix: store Math.random locally to prevent overriding it antfu/birpc#8

When users mock Math.random and do not correctly restore it back to original implementation, Vitest will freeze due to birpc being unable to pass messages.
It's wrong to not restore mocks after test execution but it's also bad to freeze the test runner.

Minimal reproduction:

beforeEach(() => {
  // Math.random is mocked but not restored after test
  vi.spyOn(Math, 'random').mockReturnValue(0.1)
})

test('Math.random is mocked', () => {
  expect(Math.random()).toBe(0.1)
})

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Vitest caught 1 unhandled error during the test run.
This might cause false positive tests. Resolve unhandled errors to make sure your tests are not affected.

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Error: [birpc] timeout on calling "onAfterSuiteRun"
 ❯ Timeout._onTimeout ../../packages/vitest/dist/vendor-index.c934bc6b.js:138:22
 ❯ listOnTimeout ../../node:internal/timers:569:17
 ❯ processTimers ../../node:internal/timers:512:7

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