labs/lab-10: Modify checkers for `read-stdin` tasks

[Alexander1752]

• Modify checkers for the tasks read-stdin-gets [1] and read-stdin-fgets [2] to check the exit code obtained by running the exploit.py script and not pass the test if the code is non-zero. In their current form, the checkers act as a blacklist for a certain string in the output of the script; if said string is not found, the checker passes the test. However, this doesn't take into account the possibility that the students' files never compiled to begin with and the script exited early due to am exception, so no output was generated to be compared with the blacklist, which makes the checkers pass the test.

Read the contributor guidelines before making contributions [3].
Add Fixes #115 at the end of your commit message to automatically link your PR with this issue.

[1] https://github.com/cs-pub-ro/hardware-software-interface/blob/main/labs/lab-10/tasks/read-stdin-gets/tests/test_read_stdin_gets.c
[2] https://github.com/cs-pub-ro/hardware-software-interface/blob/5231b9f14b33964a5f8f05507703fcb9c3cf83d2/labs/lab-07/tasks/reverse-array/support/reverse-array.asm
[3] https://github.com/cs-pub-ro/hardware-software-interface/blob/main/CONTRIBUTING.md#pull-requests