Changes imported from Abseil "staging" branch:

  - 55c7dd8ad1570b4e6ce2103ed4d4b6becdea0d96 Remove line continuations which require CMake >= 3.0.  Al... by Jon Cohen <cohenjon@google.com>
  - ee66ad72a90259d6286bbfea7241ed976bb0f6fb Change absl::ParseDuration() to avoid double.  This allow... by Abseil Team <absl-team@google.com>
  - 89cf4cd49d8ff25cb3d29f06b2090029a2024e89 Internal change by Gennadiy Rozental <rogeeff@google.com>
  - cdb5879bf6aaf6bbd2ad1fe4a2b144bbdf0389c7 Internal change by Gennadiy Rozental <rogeeff@google.com>
  - e7b29d11bf24a63bf7637689ada8be7d619844fc Internal change by Gennadiy Rozental <rogeeff@google.com>
  - 2d4fc08d5d64a7760ad6230eccdb5b8014c2b0c3 Update the exception-safety testing framework. by Jon Cohen <cohenjon@google.com>

GitOrigin-RevId: 55c7dd8ad1570b4e6ce2103ed4d4b6becdea0d96
Change-Id: I6b560cbc4570dfc5aa9a2f90e84d69904df7eac5