Remove main() from most tests.

This gives some flexibility to embedders.

Currently, embedders have to build a binary for each test file.

After this CL, embedders can still choose to have a binary for each test
file, by linking each test file with a googletest target that includes
main() (usually "gtest_main"). Embedders can also choose to build a
single binary for almost all test files, and link with a googletest
target that includes main(). The latter is more convenient for projects
that have very few test binaries, like Chromium.

PiperOrigin-RevId: 419470798

db/write_batch_test.cc

@@ -130,8 +130,3 @@ TEST(WriteBatchTest, ApproximateSize) {
 }
 
 }  // namespace leveldb
-
-int main(int argc, char** argv) {
-  testing::InitGoogleTest(&argc, argv);
-  return RUN_ALL_TESTS();
-}