tools/libxc: Drop dombuilder support for PV autotranslate guests

tools/libxc: Drop dombuilder support for PV autotranslate guests

c/s 4045953 "x86/paging: Enforce PG_external == PG_translate == PG_refcounts"
in the hypervisor finally prevented the construction of PV autotranslate
guests.

Remove support for such guests in the domain builder, bailing out with an
obvious "no longer supported" message, rather than a more obscure
"SHADOW_OP_ENABLED failed".

As a piece of cleanup, rename xc_dom_feature_translated() to
xc_dom_translated() to match its actual semantics.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>