Handle nullability of detail correctly in performance.mark and performance.measure (#52557)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/52557

Changelog: [internal]

`PerformanceEntry.detail` should be `null` if not defined, not undefined as it is currently. This fixes that.

Reviewed By: hoxyq

Differential Revision: D78013568

fbshipit-source-id: b22dfdd8d582594fc1e5199264e8af92c26bb0ea