message: [vm] avoid a vector clone in deserializer
  Use `String::from_utf8`.
diff: @@ -7,7 +7,6 @@ use std::{
  collections::HashSet,
  convert::TryInto,
  io::{Cursor, Read},
  - str::from_utf8,
  };
  use types::{account_address::ADDRESS_LENGTH, byte_array::ByteArray};
  @@ -523,12 +522,12 @@ fn load_string_pool(
  if count != size {
  return Err(BinaryError::Malformed);
  }
  - let s = match from_utf8(&buffer) {
  + let s = match String::from_utf8(buffer) {
  Ok(bytes) => bytes,
  Err(_) => return Err(BinaryError::Malformed),
  };
  - strings.push(String::from(s));
  + strings.push(s);
  }
  }
  Ok(())
  