vte: Build without vala by default

vte: Build without vala by default

vala.bbclass DEPENDS on vala and vala-native: Drop the inherit so
that these dependencies can be added on-demand based on vte
PACKAGECONFIG. Add relevant items from vala class into the recipe.

Add copy of vapigen.m4 so building without vala actually succeeds.

Make building without vala the default PACKAGECONFIG.

Fixes [YOCTO #10386].

(From OE-Core rev: 516b5c407e19029c09b870d460f64b7133f742b4)

Signed-off-by: Jussi Kukkonen <jussi.kukkonen@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>