abseil: add 20200923 + generate components helper file during packaging

[SpaceIm]

Specify library name and version: abseil/all

• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[conan-center-bot]

Some configurations of 'abseil/20200923' failed in build 1 (3b466dd2d37560100277d09889effb9e33a691af):

• Macos x86_64, Release, apple-clang 9.1, libc++
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• Macos x86_64, Release, apple-clang 10.0, libc++
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• Macos x86_64, Release, apple-clang 11.0, libc++
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• Macos x86_64, Debug, apple-clang 9.1, libc++
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• Macos x86_64, Debug, apple-clang 11.0, libc++
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• Macos x86_64, Debug, apple-clang 10.0, libc++
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• Linux x86_64, Release, clang 3.9, libstdc++
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[conan-center-bot]

All green in build 2 (c695a4dde76df367ec0007e8d54c5153e15bb63d)! 😊

• abseil/20200205: Generated 68 packages. All logs here
• abseil/20200225.2: Generated 68 packages. All logs here
• abseil/20200923: Generated 68 packages. All logs here

[prince-chrismc]

Wow.

[conan-center-bot]

All green in build 3 (7f13c99b581772535501895386bca60213b9dc46)! 😊

• abseil/20200205: Generated 68 packages. All logs here
• abseil/20200225.2: Generated 68 packages. All logs here
• abseil/20200923: Generated 68 packages. All logs here

[Croydon]

@jgsogo Seems like we have another situation here. 3 approvals and build successful, but no merge yet