Export of internal Abseil changes

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8e04df6fcbd062e5eaf179a6ec9b0a26f8aa8a39 by Abseil Team <absl-team@google.com>:

Use a floating point type for the example usage of absl::uniform_real_distribution.

PiperOrigin-RevId: 271167776

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5f8f1dfea50bc16a9d9af3e50c4636500a938b29 by Abseil Team <absl-team@google.com>:

the llvm wasm backend does not support this data symbol in text section, so remove it from the test.

PiperOrigin-RevId: 271138100

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2874542cb212962ac3093fd78fd5e1eb85c126c0 by Xiaoyi Zhang <zhangxy@google.com>:

Work around MSVC 2019 compiler bug related to constexpr in optional_test.
The change in optional_test is necessary to avoid another bug on MSVC
complaining about accessing invalid member of union, and also makes the test
more reasonale by checking the value of a non-static member.

Filed a bug against MSVC
https://developercommunity.visualstudio.com/content/problem/743998/internal-compiler-error-related-to-constexpr-and-u.html.

PiperOrigin-RevId: 271129805

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3a5d56f0c3362aabf68938fb95c4e2d3eca59538 by Abseil Team <absl-team@google.com>:

Improve precision of absl::GetCurrentTimeNanos() by adjusting
cycle time sooner.

PiperOrigin-RevId: 271007945

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1e044a6dec7c0ca150fff1aee52dbdb16aa43ed7 by Abseil Team <absl-team@google.com>:

Internal change.

PiperOrigin-RevId: 270962690
GitOrigin-RevId: 8e04df6fcbd062e5eaf179a6ec9b0a26f8aa8a39
Change-Id: Icb05423a7e93ebdae16baadd59a60b75b5cfa249