Create shorthand for including all extra tests

Hi,

I realized that I forgot to add the new extra test to my test scripts.
So, I thought maybe we can use shorthand for including all extra
tests. With that, running a full testsuite is easier without having to
keep up with new tests and updates.

I created an 'all' option for PG_TEST_EXTRA to enable all test suites
defined under PG_TEST_EXTRA. I created the check_extra_tests_enabled()
function in the Test/Utils.pm file. This function takes the test's
name as an input and checks if PG_TEST_EXTRA contains 'all' or this
test's name.

I thought another advantage could be that this can be used in CI. But
when 'wal_consistency_checking' is enabled, CI times get longer since
it does resource intensive operations.

Any kind of feedback would be appreciated.

Regards,
Nazir Bilal Yavuz
Microsoft