Unify the case, punctuation and name of test case keywords so they can
be more easily selected or skipped when desired. Add a few keywords that
were missing. Fix a couple of typos in test names.
To make it uniform in all tests, and greppability.
Also:
- replace `-k` flag with `-q` in test 1268. (the actual flag doesn't
matter in this test)
- keep `-k` in test 300 to test its short form.
(also verified to fail without a working `-k`)
Closes#16878
The threee tags `<name>`, `</name>` and `<command>` were frequently used
with a leading space that this removes. The reason this habbit is so
widespread in testcases is probably that they have been copy and pasted.
Hence, fixing them all now might curb this practice from now on.
Closes#12028
