Increase block_conversion_test shards from 10 to 50. It is the long pole when testing with asan/msan. Test time dropped from >600s to ~150s.
Increase block_conversion_test shards from 10 to 50.
It is the long pole when testing with asan/msan. Test time dropped from >600s to ~150s.

PiperOrigin-RevId: 453497644

google/xls,google/xls,google/xls,google/xls,google/xls,google/xls