Let `before_test` and `after_test` to set hooks for several tests

[Steap2448]

Sometimes there is a need to set one hook for several tests. As a result you have to write before_test and after_test with the same function for each test individually and it produces a lot of unnecessary code.

It would be nice to have an ability to do it in one command. Let's allow before_test and after_test to set one hook for several tests in such way:

g.before_test({'test_1, test_2'}, function() ... end)

[yngvar-antonsson]

What's difference between

g.before_test({'test_1, test_2'}, function() ... end)

and

group1.before_each(, function() ... end)
group2.before_each(, function() ... end)

?

[Steap2448]

g.before_test({'test_1, test_2'}, function() ... end)

Hook is defined for test_1 and test_2 of the group g only

group1.before_each(, function() ... end)
group2.before_each(, function() ... end)

Hook is defined for all tests from groups group1 and group2.