transport: Add a capsfilter after the encoder

And repurpose the now unused _owr_payload_create_encoded_caps() to
get the caps for it.

Here we now tell the encoder to create streams with a specific
profile or level. Currently this is only done for H264 to enforce
baseline profile, as anything else might not be supported by decoders.
transport: Disable passthrough mode in h264parse

Currently the detection if we actually can do passthrough or not
is broken in h264parse. It would go into passthrough mode in some
cases where we would really need h264parse to extract information
from the bitstream for us.