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ARROW-15671: [GLib] Add support for Vala

Closes #12993 from kou/glib-vapi

Lead-authored-by: Sutou Kouhei <kou@clear-code.com>
Co-authored-by: Tao Zuhong <taozuhong@users.noreply.github.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>