[Execute Shell Command] Fix return type inconsistency and print formatting bug

[Prayas340]

Description

In Execute Shell Command/execute_shell_command.py:

1. When an exception occurs during shell command execution, execute_shell_command(command) returns a single integer (105) instead of a tuple (bytes, int). Callers unpacking result, status = execute_shell_command(command) crash with TypeError: cannot unpack non-iterable int object.
2. Line 14 uses comma-separated formatting print("Exception Occurred while executing module : %s", str(err)), which prints the formatting string literally instead of substituting %s.
3. execute_shell_command_test.py lacks coverage for failed commands.

Proposed Fix

• Update return statement in except block to return (b'', 105).
• Use f-string formatting for exception printing.
• Add unit test for failed execution in execute_shell_command_test.py.