tests: Add test for pyb.disable_irq and pyb.enable_irq.

tests/pyb/irq.py

+import pyb
+
+def test_irq():
+    # test basic disable/enable
+    i1 = pyb.disable_irq()
+    print(i1)
+    pyb.enable_irq() # by default should enable IRQ
+
+    # check that interrupts are enabled by waiting for ticks
+    pyb.delay(10)
+
+    # check nested disable/enable
+    i1 = pyb.disable_irq()
+    i2 = pyb.disable_irq()
+    print(i1, i2)
+    pyb.enable_irq(i2)
+    pyb.enable_irq(i1)
+
+    # check that interrupts are enabled by waiting for ticks
+    pyb.delay(10)
+
+test_irq()

tests/pyb/irq.py.exp

+True
+True False