OwrImageRenderer: Add a queue to decouple conversion from decoding

Previously there was one thread from the jitterbuffer through to the
sink. Use max-size-buffers = 3 as the limiting factor to allow a bit of
scheduling room.
owr_utils: Remove chatty and not-useful pipeline debug log

This is too hard to read and dot graphs are much easier to use.
OwrImageRenderer: Compare double max framerate to 0.0, not 0
OwrVideoRenderer: Fix queue max-size-time guint64 property
OwrTransportAgent: Fix queue properties

max-size-time is a guint64 so the constant needs to also be
G_GUINT64_CONSTANT()-ified. Also set max-size-buffers to 3 to give a bit
of scheduling room.
transport: Set the correct properties for other H264 encoders than OpenH264

x264enc and vtenc_h264 take the bitrate property in kbit/s instead of
bit/s, and x264enc should be set to zero-latency mode for realtime
communication.
transport: Remove unused capsfilter element

This is not added to the pipeline or used in any other way.
transport: Remove capsfilter after depayloader and add parser before videorepair

The capsfilter would cause stream format conversion twice in the worst case,
and in the best case have no effect at all. However adding a parser in front
of videorepair is a good idea so that we're guaranteed to have keyframes
marked correctly.
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.
owr: Use dashes in GObject property names, not underscores

GObject converts them for us but let's do that work on our side once.
Update scripts

Minor fixes only
OwrImageRenderer: Limit frame rate using videorate max-rate

If we use videorate with max-rate and drop-only=true, we should be able
to apply framerate limitations without adding any latency. This also
avoids caps negotiation issues with drop-only=true, input caps as 0/1 or
just generally having higher output framerate than input.
OwrLocalMediaSource: Improve frame rate limiting

Use drop-only=true max-rate=fps to limit video frame rate with zero
latency.
OwrVideoRenderer: Remove unnecessary conversion elements

glimagesink can do colour space conversion and scaling itself. Unless
we're at the limits of performance with high framerate and high
resolution, limiting framerate is unnecessary.
OwrVideoRenderer: Make queue downstream leaky
OwrImageRenderer: Rename elements to image-renderer-*
OwrImageRenderer: Set constraining caps
transport_agent: Asynchronously resolve the helper server address
Fix API entry point prefixes.