Add TestWatchdog, Tripwire

[carbolymer]

This PR adds a TestWatchdog and Tripwire and their test. A sample tripwire check output looks like this:

         86 ┃   -- make sure that we didn't trigger the tripwire
         87 ┃   H.assertNotTripped childTripwire
            ┃   │ Tripwire 2 has been tripped at: CallStack (from HasCallStack):
            ┃   │   tripTripwire, called at test/Hedgehog/Extras/Test/TestWatchdogSpec.hs:84:5 in main:Hedgehog.Extras.Test.TestWatchdogSpec
            ┃   │   testCase, called at src/Hedgehog/Extras/Test/TestWatchdog.hs:124:66 in hedgehog-extras-0.6.2.0-inplace:Hedgehog.Extras.Test.TestWatchdog
            ┃   │   testCase, called at src/Hedgehog/Extras/Test/TestWatchdog.hs:116:11 in hedgehog-extras-0.6.2.0-inplace:Hedgehog.Extras.Test.TestWatchdog
            ┃   │   runWithWatchdog, called at src/Hedgehog/Extras/Test/TestWatchdog.hs:124:36 in hedgehog-extras-0.6.2.0-inplace:Hedgehog.Extras.Test.TestWatchdog
            ┃   │   runWithWatchdog_, called at test/Hedgehog/Extras/Test/TestWatchdogSpec.hs:66:31 in main:Hedgehog.Extras.Test.TestWatchdogSpec
            ┃   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
         88 ┃   H.assertNotTripped grandChildTripwire1
         89 ┃   H.assertNotTripped grandChildTripwire2