Added exit code for failure of tests

[Krishna-13-cyber]

This PR will give the exit codes for the failure of tests.In case of failure of any of the tests,it will exit and it indicates that the particular test has some error/bug in it while execution.

[VedantParanjape]

@Krishna-13-cyber please add a proper PR description as well

[VedantParanjape]

ot running on a BeagleBone
Running test  boolean.sim
b'1\n1\n1\n1\n1\n0\n'
Test boolean.sim passed
Running test  datatypes.sim
b'Initialized by default to 0\nInitialized by default to false\nNow 2\nStill 2\ntrue\n15\n1194639\n241\n-226\n97\n65\n66\n8\n'
Test datatypes.sim passed
Running test  ifelse.sim
b'inside if\nshould be printed\n'
Test ifelse.sim passed
Running test  comparison.sim
b'0\n0\n1\n1\n0\n0\n0\n1\n0\n1\n1\n1\n1\n0\n1\n0\n1\n1\n'
Test comparison.sim passed
Running test  arrays.sim
b'ok\n720108101\n'
Test arrays.sim passed
Running test  print.sim
b'Start with newline\nPrinting! inside, with newline\n5\n0\n10 is the value of b\n4\n'
Test print.sim passed
Running test  arithmetic.sim
b'-584\n30\n33\n2\n260\n19\n18\n361\n2\n1\n4\n2\n96\n31\n-2147483648\n11\n9910099\n'
**** ****TEST FAILED**** ****: arithmetic.sim
b'-584\n30\n33\n2\n260\n19\n18\n361\n2\n1\n4\n2\n96\n31\n-2147483648\n11\n9910099\n'
b'-584\n30\n33\n2\n260\n19\n18\n361\n2\n1\n4\n2\n96\n31\n0\n11\n9910099\n'

this test output is quite bad looking, can you prettify it if possible.