FEI: Add codec objects for fei usecase

FEI: Add codec objects for fei usecase

There are 6 new va buffer types, each defined as a specific codec object.
Borrowed the code from gstvaapicodecobject , but made a clear separation
to avoid any possible mess-up. Because unlike the other gstvaaicodecobjects,
feicodecobjects can be shared between elements and also can be accessed
from different thread.

Unlike the other fei codecs object, VAEncMiscParameterTypeFEIFrameControl
object is not shared between elements.So we utilize the already
existing gst_vaapi_enc_misc_param_new(), but still keeping the code
in gstvaapfei_objects_priv.h in order to have a better
code readability.

Fixme:
-- Probably we need _locked_map() and _unlocked_map()
-- Context can be associated with PreEnc(not just Enoder)
once we have the proper support inplace, but for now we don't have
PreEnc support, so should be safe enough to use GstVaapiEncoder.

https://bugzilla.gnome.org/show_bug.cgi?id=785712
https://bugzilla.gnome.org/show_bug.cgi?id=784667