ci.kaitai.io: use snake_case for test names instead of PascalCase

[Mingun]

The original KSY specifications is written in snake_case, but in the test matrix at https://ci.kaitai.io/ test names converted to PascalCase. It makes quite difficult to find a source KSY to check the test.

Even better, if test name would by hyperlink to the file in github repository at time of matrix building.

[generalmimon]

Even better, if test name would by hyperlink to the file in github repository at time of matrix building.

You already suggested this: kaitai-io/kaitai_ci_ui#4