Revert "Add Abseil to third_party."

This reverts commit 816226e822635011c4e9dae6fb1d5ed8113bfbfd.

Reason for revert: 

https://chromium-swarm.appspot.com/task?id=4bc69ffc0a889110

/mnt/pd0/s/w/ir/clang_linux/bin/clang++ -rdynamic -Wl,-rpath,\$ORIGIN --target=armv7a-linux-gnueabihf --sysroot=/mnt/pd0/s/w/ir/armhf_sysroot -static-libstdc++ -static-libgcc -B/mnt/pd0/s/w/ir/armhf_sysroot/bin -B/mnt/pd0/s/w/ir/armhf_sysroot/gcc-cross -L/mnt/pd0/s/w/ir/armhf_sysroot/gcc-cross -L/mnt/pd0/s/w/ir/armhf_sysroot/lib -L/mnt/pd0/s/w/ir/chromebook_arm_gles/lib -Wl,--start-group @./dm.rsp  -Wl,--end-group -lpthread -ldl -lGLESv2 -lEGL -o ./dm
libabsl.a(libabsl.numbers.o): In function `absl::string_view::substr(unsigned int, unsigned int) const':
/mnt/pd0/s/w/ir/skia/third_party/externals/abseil-cpp/absl/strings/string_view.h:387: undefined reference to `absl::base_internal::ThrowStdOutOfRange(char const*)'
clang-10: error: linker command failed with exit code 1 (use -v to see invocation)


Original change's description:
> Add Abseil to third_party.
> 
> At present, this is a proof-of-concept which only supports a small
> subset of absl modules:
> - Base
> - Hash
> - Numeric
> - String
> 
> This is only used by one unit test, which builds a string and then
> hashes it.
> 
> Bug: skia:10165
> Bug: b/154848688
> 
> Change-Id: I016250bf700b522c7a6bc78cf1844abff2260c35
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/284805
> Reviewed-by: Derek Sollenberger <djsollen@google.com>
> Commit-Queue: John Stiles <johnstiles@google.com>
> Auto-Submit: John Stiles <johnstiles@google.com>

TBR=djsollen@google.com,johnstiles@google.com

Change-Id: If9936f1beaf6ac9c85718ce445e823bf2f57a6fa
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:10165, b/154848688
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/285491
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
5 files changed