adapter: Copy over GstMeta from the input buffers to the output

adapter: Copy over GstMeta from the input buffers to the output

All functions that return a GstBuffer or a list of them will now copy
all GstMeta from the input buffers except for meta with GST_META_FLAG_POOLED
flag or "memory" tag.

This is similar to the existing behaviour that the caller can't assume
anything about the buffer flags, timestamps or other metadata. And it's
also the same that gst_adapter_take_buffer_fast() did before, and what
gst_adapter_take_buffer() did if part of the first buffer or the complete
first buffer was requested.

https://bugzilla.gnome.org/show_bug.cgi?id=742385