Imported from GitHub PR https://github.com/abseil/abseil-cpp/pull/1643

Addressing comments at https://github.com/abseil/abseil-cpp/pull/1604/#pullrequestreview-1937008657
Add a xcprivacy subspec and have all other subspecs depend on it (option 1)

Didn't going with option 3 because there are several levels of subspecs in abseil podspec, it's difficult to track whether all of them directly or indirectly depends on abseil/base/config or ensure they will continue to depend on it.

Example of generated podsped: https://gist.github.com/HannahShiSFB/15d8fb6aa637f2781b7be4218d080f11
Merge 4405cdfe71129bebb13c02a6d8ee18be7e813f73 into 4539c540

Merging this change closes #1643

COPYBARA_INTEGRATE_REVIEW=https://github.com/abseil/abseil-cpp/pull/1643 from HannahShiSFB:privacy-manifests 4405cdfe71129bebb13c02a6d8ee18be7e813f73
PiperOrigin-RevId: 616914674
Change-Id: If56d5a4f1a7cc6f9fac7a2d8e95b55d140e645fc