[Executor] Fix vm_execute_block_time counter
[Executor] Fix vm_execute_block_time counter

`vm_execute_block_time_us` was added to the wrong place where it should be `execute_chunk`.

libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core