Log Message:
abseil: updated to 20230802.0

Abseil LTS 20230802

What's New:

Added the nullability library for designating the expected nullability of \ 
pointers. Currently these serve as annotations only, but it is expected that \ 
compilers will one day be able to use these annotations for diagnostic purposes.
Added the prefetch library as a portable layer for moving data into caches \ 
before it is read.
Abseil's hash tables now detect many more programming errors in debug and \ 
sanitizer builds.
Abseil's synchronization objects now differentiate absolute waits (when passed \ 
an absl::Time) from relative waits (when passed an absl::Duration) when the \ 
underlying platform supports differentiating these cases. This only makes a \ 
difference when system clocks are adjusted.
Abseil's flag parsing library includes additional methods that make it easier to \ 
use when another library also expects to be able to parse flags.
absl::string_view is now available as a smaller target, \ 
@com_google_absl//absl/strings:string_view, so that users may use this library \ 
without depending on the much larger @com_google_absl//absl/strings target.