Make test names and descriptions more consistent

Most core test descriptions use the language "Test X" or "Tests X". Switched to the former.

Also, removed unnecessary translation of description.

Test names were inconsistent in capitalization. The word "test" is not used by many core tests, so dropped.

Maybe "password" could be dropped from the test names. (It would be obvious what "Constraints" is testing. Shouldn't be necessary to specify that they are "Password constraints".) However, left "password" for consistency with 7.x-1.x/6.x-1.x.

Used slightly pithier wording in description.