This way we can have a single file that wraps scenarios,
`gst-validate-1.0` arguments, as well as a configuration.

It changes the name of `description` of scenarios to use `meta`
The goal is to replace tests describes in python with dictionary
to fully self contained `.validatetest` files which look like:

```
meta,
    handles-states=true,
    ignore-eos=true,
    gst-validate-args = {
         "videotestsrc pattern=blue ! video/x-raw,format=I420,framerate=1/1 ! timeoverlay ! $(videosink) name=videosink allocation-meta-flags=0",
    },
    configs = {
         "$(validateflow), pad=videosink:sink, buffers-checksum=true, ignored-fields={\"buffers=meta\", }",
    }

play
seek, start=0.0, stop=5.0, flags=accurate+flush, rate=1.0
crank-clock, expected-elapsed-time=0.0
crank-clock, repeat=4, expected-elapsed-time=1.0
crank-clock, expected-elapsed-time=1.0
stop, on-message=eos
```