Make it possible to mock @Resource injection point easily

[mkouba]

A CDI bean in test might declare non-CDI injection points, e.g.:

class Foo {
    @Resource(lookup = "bar")
    String bar;
    
    void ping() {
      // use bar..
    }
}

It should be possible to mock those injection points easily. Right now, the only way is to implement injection services SPI (see also http://docs.jboss.org/weld/reference/latest/en-US/html/ri-spi.html#_ee_resource_injection_and_resolution_services).