third_party/googletest: use gtest-all.cc and gmock-all.cc
third_party/googletest: use gtest-all.cc and gmock-all.cc

Upstream googletest has refactored googletest's assertion result into
gtest-assertion-result.h and gtest-assertion-result.cc. To avoid future
issues, only use gtest-all.cc and gmock-all.cc as source files.

Bug: 660, b/228906345
Change-Id: Ib7756f78a6d416079db14445ea22778a3631936e
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/92500
Reviewed-by: Wyatt Hepler <cca3bedb37979eacd157a9bceb473582df8aea1e@google.com>
Reviewed-by: Ted Pudlik <c7372cc3e451acc046049fca9e050bcb2a4a3d11@google.com>
Pigweed-Auto-Submit: Jonathan Cardy <b541952bb80ecc8bd0f16a279d10badd687d1513@google.com>
Commit-Queue: Auto-Submit <14637eda5603879df170705285bf30f5996692f0@pigweed.google.com.iam.gserviceaccount.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed