[LTP] [PATCH v2] doc: add tests catalog page

[Petr Vorel]

Hi Andrea,

first, thanks for doing the migration.
I haven't checked whether all necessary keys are shown (will do).

It would be nice, if the keys (e.g. mount_device) were references, then user can
click to the documentation.

I'm also thinking that splitting tests by alphabet would help to have shorter
page + not that long list of the tests on the left side. But for searching it's
better to have all tests on a single page. WDYT?

Kind regards,
Petr