Update to abseil-cpp 20250512.1

[HannahShiSFB]

Sync from https://github.com/abseil/abseil-cpp/releases/tag/20250512.1
Removed all test and benchmark files:

rm -rf `find absl/ -name "*_test.cc"`
rm -rf `find absl/ -name "*_test.c"`
rm -rf `find absl/ -name "*_benchmark.cc"`
rm absl/status/internal/status_matchers.*
rm -rf absl/time/internal/cctz/testdata
rm -rf `find absl/ -name "BUILD.bazel"`
rm -rf `find absl/ -name "CMakeLists.txt"`
rm -rf absl/copts
rm -rf `grep -rl '#include "gtest/gtest.h"'`
rm -rf `grep -rl '#include "gmock/gmock.h"'`
rm -rf `grep -rEl "^int main\(" absl/`

Tested with

swift build
swift test

For gRPC dependency
CC: @sampajano @stanley-cheung

[ncooke3]

cc: @cherylEnkidu

[ncooke3]

Thanks @HannahShiSFB ! I've published the 0.20250512.1 tag