Update to latest google3 version

[jmr]

• Remove glog and gflags dependencies. Now abseil-cpp is used.
  • ABSL_LOG macros are used instead of S2_LOG
  • The indirection could be added back if requested
  • ABSL_CHECK macros are used instead of S2_CHECK
  • S2DEFINE now forwards to ABSL_FLAG
• New files:
  • s2chain_interpolation_query
  • s2density_tree
  • s2gmock_matchers
  • s2fractal
  • s2shapeutil_count_vertices
  • s2shapeutil_edge_wrap
• Requires abseil-cpp LTS 20240116
• New S2Shape functions:
  • Incoming
  • Outgoing
  • IncidentOn
• Remove S2Shape::id()
• New predicates in s2predicates.h
• S2Region::GetCellUnionBound is now pure virtual

[smcallis]

Whooo thanks Jesse.

[iljya]

I believe that after this commit, the project no longer compiles with C++14. At least I got errors with this file: src/s2/util/gtl/requires.h

With C++17 it works. C++14 is claimed to be supported in a number of places, like the README and CMakeLists.txt. I'm not sure if this was intended and simply the documentation should be updated, or not intended.

[jmr]

That's a mistake. I'll make a new PR soon.