Add meson feature options for Spice and Spice protocol, and move
detection logic out of configure.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20211007102453.978041-1-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20211007130829.632254-13-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>