Add lcm function and its tests to NumPy Frontend

[shauryabhawaker]

Close #15700

[iamjameskeane]

LGTM!

Test failures are due to code elsewhere in the project.

Thanks! :)

[shauryabhawaker]

@jkeane508 First error is due to other function,

available_dtypes=helpers.get_dtypes("int"),

could the error be due to this?

This is what im getting in the git test results. But it is only for the paddle backend.
________ test_numpy_lcm[cpu-ivy.functional.backends.paddle-False-False] ________
ivy_tests/test_ivy/test_frontends/test_numpy/test_mathematical_functions/test_miscellaneous.py:680: in test_numpy_lcm
fn_tree="numpy.lcm",
ivy_tests/test_ivy/helpers/hypothesis_helpers/array_helpers.py:490: in dtype_and_values
available_dtypes = draw(available_dtypes)
/opt/miniconda/envs/multienv/lib/python3.8/site-packages/hypothesis/internal/conjecture/data.py:950: in draw
return strategy.do_draw(self)
/opt/miniconda/envs/multienv/lib/python3.8/site-packages/hypothesis/strategies/_internal/core.py:1510: in do_draw
return self.definition(data.draw, *self.args, **self.kwargs)
ivy_tests/test_ivy/helpers/hypothesis_helpers/dtype_helpers.py:173: in get_dtypes
valid_dtypes = set(retrieval_fn(test_globals.CURRENT_BACKEND(), kind))
ivy_tests/test_ivy/helpers/hypothesis_helpers/dtype_helpers.py:35: in _get_fn_dtypes
return test_globals.CURRENT_RUNNING_TEST.supported_device_dtypes[framework.backend][
E KeyError: 'int'
E
E You can reproduce this example by temporarily adding @reproduce_failure('6.75.3', b'AA==') as a decorator on your test case