[move source language] Added help to ir_test_coverage
[move source language] Added help to ir_test_coverage

Closes: #2883
Approved by: shazqadeer

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