[executor] trivial: refactor TestBlock
[executor] trivial: refactor TestBlock

1. The constructor takes in a size, instead of a range (which is never useful)
2. expect that the resulting block size being different from the number of user transactions (because we are gonna append the state checkpoint txn)

Closes: #10161

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