Export of internal Abseil changes.

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788c948f698afe5998738cbb40b0629668640d73 by Derek Mauro <dmauro@google.com>:

Add an empty raw_logging_internal library. The raw_logging sources
will eventually migrate here.

This target will only contain internal sources. Abseil compatibility
guidelines require users not depend on internals.
https://abseil.io/about/compatibility

PiperOrigin-RevId: 260712817

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8ea947ec54f47fb02e97597d243cb63aa4c5fe0b by Abseil Team <absl-team@google.com>:

Fixed an incorrect version number test for optional,etc. availability
in iOS. Added tests for watchOS and tvOS.

PiperOrigin-RevId: 260490390

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53af0544277dc3020b81d16ce110e7bc89f5cf6e by Jorg Brown <jorg@google.com>:

Test the error-string path a bit more.

PiperOrigin-RevId: 260175886
GitOrigin-RevId: 788c948f698afe5998738cbb40b0629668640d73
Change-Id: I366b73331857dc5a1db843b650c2ba27a69a141e