Improve decide allocation so it properly configure both local and downstream
buffer pools. Also read back the pool config if it was changed to to driver
limitations.

Pre-configuring the pool is error prone, since it may hide a configuration failure and
endup with a pool that is not configured the way it should (e.g. no video meta, wrong
queue size, etc.)

Turn crop meta into a custom option and make sure it's there is needed.

Catch short allocation after saving the format. This is not a catch all, but should catch
most of the miss-behaving drivers when doing S_FMT/G_FMT and avoid potential crash.

This goal of this allocator is mainly to allow tracking the memory.
Currently, when a buffer memory has been modified, the buffer and it's
memory is disposed and lost until the stream is restarted.

Currently we advertise crop meta, but not element handle support this meta.

Some well known decoder wrongly set num_planes to 0 in their format instead of
one. In this case we would endup with no size when deciding buffer allocation.

All the element requires at least two buffers. This is not used for RW mode.

This should remove 1 copy between the decoder and the transform.

That pool may be different then the internal pool.

Implement a v4l2 element that wraps HW video converters.

In order to correctly set the pool min/max, we need to probe for CREATE_BUFS
ioctl. This can be done as soon as the format has been negotiated using a
count of 0.

Now that we might be copying out buffer (e.g. downstream don't support video
meta bug we need it) we need to move the EOS handling inside the process
method.

So far we where only setting saving the first plane stride in the meta. This was
leading to wrong values in GstVideoMeta.

As soon a the alpha component can be set, we can expose the RGB32 and BGR32
format as ARGB and BGRA as long we can deterministically set the alpha padding
value.

Correctly check if video meta is needed. In buffer pool, trust need_video_meta
flag in order to decide if configuration should succeed.

Fix stride request for tiled format and improve logging.

In certain cases we cannot live without video meta and/or crop meta
being enabled in our internal buffer pool. Ensure this is always the case,
regardless of having support for allocation query.

Upon error, the pools might not have been allocated yet, hence we should not
try and flush them (even though we still want to make sure the processing thread
is fully stopped).

Enforce pool being activate from before calling pool process. This should
help catching basic errors in the usage of buffer pool.