[test] Stop leaking mocked performance clocks into later test files

[eps1lon]

Test files running in the Node.js Jest environment share the worker process's performance object, because jest-environment-node installs it by reference rather than by copy. When a test mocked the clock with Object.defineProperty(performance, 'now', ...), the mutation hit the shared object and was never undone, since Jest only restores jest.spyOn mocks when a file's runtime is torn down (jest-runtime's teardown() calls restoreAllMocks()). Every subsequent test file in the same worker then observed the fake clock, including jsdom-based files, whose performance.now() subtracts a window-creation timestamp from the shared object's now().

This change switches the six affected test files to jest.spyOn(performance, 'now') and jest.spyOn(performance, 'timeOrigin', 'get'), which Jest restores automatically at teardown. ReactFlightDOMEdge-test.js runs in jsdom and therefore did not leak, but it used the same pattern and is converted for consistency.

This change is mostly for test hygiene. Was discovered while investigating a flaky {"time":NaN} serialisation bug (e.g. https://github.com/react/react/actions/runs/32878999825/job/97903912119)

[github-actions]

Comparing: 373d35e...c71633e

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-stable/react-dom/cjs/react-dom.production.js	=	7.35 kB	7.35 kB	=	1.96 kB	1.96 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	622.22 kB	622.22 kB	=	110.01 kB	110.01 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	7.36 kB	7.36 kB	+0.05%	1.96 kB	1.96 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	693.43 kB	693.43 kB	=	121.46 kB	121.46 kB
facebook-www/ReactDOM-prod.classic.js	=	713.60 kB	713.60 kB	=	124.94 kB	124.94 kB
facebook-www/ReactDOM-prod.modern.js	=	703.91 kB	703.91 kB	=	123.36 kB	123.36 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

_{Generated by sizebot against c71633e}