Clean up code around Prometheus metrics, more DRY.
Clean up code around Prometheus metrics, more DRY.

With this change, all definitions and functionality for a given metric
are in a single place only instead of being distributed all over the
file. This makes it easier to inspect the code for correctness and
adding/changing metrics.

aivarasko/cadvisor,ChengTiesheng/cadvisor,IFTTT/cadvisor,IFTTT/cadvisor,vmarmol/cadvisor,f0/cadvisor,megamsys/cadvisor,derekwaynecarr/cadvisor,difro/cadvisor,takecy/cadvisor,hzy001/cadvisor,wulonghui/cadvisor,BrickXu/cadvisor,jzaefferer/cadvisor,vmarmol/cadvisor,yifan-gu/cadvisor,bowlofstew/cadvisor,f0/cadvisor,jimonreal/cadvisor,hacpai/cadvisor,linux-on-ibm-z/cadvisor,rajthilakmca/cadvisor,erSitzt/cadvisor,takecy/cadvisor,ncdc/cadvisor,Snorch/cadvisor,carmark/cadvisor,mr-justin/cadvisor,derekwaynecarr/cadvisor,Snorch/cadvisor,whosthatknocking/cadvisor,c-st/cadvisor,hzy001/cadvisor,rajthilakmca/cadvisor,morpheyesh/cadvisor,atyenoria/cadvisor,hw-qiaolei/cadvisor,ainsleyc/cadvisor,Clever/cadvisor,atyenoria/cadvisor,anarcher/cadvisor,vishh/cadvisor,dchen1107/cadvisor,feiskyer/cadvisor,cnaize/cadvisor,BrickXu/cadvisor,mr-justin/cadvisor,jimonreal/cadvisor,kmicheal/cadvisor,jhjeong-kr/cadvisor,feiskyer/cadvisor,erSitzt/cadvisor,ncdc/cadvisor,mangalaman93/cadvisor,timstclair/cadvisor,feiskyer/cadvisor,ainsleyc/cadvisor,jimonreal/cadvisor,normanjoyner/cadvisor,datawisesystems/cadvisor,guoshimin/cadvisor,jhjeong-kr/cadvisor,IFTTT/cadvisor,pwittrock/cadvisor,bing6/cadvisor,morpheyesh/cadvisor,jimmidyson/cadvisor,timstclair/cadvisor,vegasbrianc/cadvisor,mangalaman93/cadvisor,difro/cadvisor,jzaefferer/cadvisor,hacpai/cadvisor,dchen1107/cadvisor,CrazyJvm/cadvisor,derwolfe/cadvisor,normanjoyner/cadvisor,hw-qiaolei/cadvisor,pwittrock/cadvisor,bowlofstew/cadvisor,bing6/cadvisor,hw-qiaolei/cadvisor,mesosphere/cadvisor,Clever/cadvisor,dchen1107/cadvisor,jhjeong-kr/cadvisor,guoshimin/cadvisor,yifan-gu/cadvisor,cnaize/cadvisor,dalanlan/cadvisor,erSitzt/cadvisor,jimmidyson/cadvisor,afein/cadvisor,pwittrock/cadvisor,mr-justin/cadvisor,anarcher/cadvisor,IFTTT/cadvisor,whosthatknocking/cadvisor,Snorch/cadvisor,vmarmol/cadvisor,dchen1107/cadvisor,ChengTiesheng/cadvisor,derekwaynecarr/cadvisor,bpradipt/cadvisor,wulonghui/cadvisor,yolkov/cadvisor,shilpamayanna/cadvisor,f0/cadvisor,IFTTT/cadvisor,carmark/cadvisor,cnaize/cadvisor,Clever/cadvisor,ainsleyc/cadvisor,yolkov/cadvisor,vishh/cadvisor,derekwaynecarr/cadvisor,jmaitrehenry/cadvisor,anarcher/cadvisor,ChengTiesheng/cadvisor,linux-on-ibm-z/cadvisor,erSitzt/cadvisor,vegasbrianc/cadvisor,aivarasko/cadvisor,BrickXu/cadvisor,jhjeong-kr/cadvisor,dalanlan/cadvisor,wulonghui/cadvisor,jzaefferer/cadvisor,jmaitrehenry/cadvisor,kmicheal/cadvisor,jhjeong-kr/cadvisor,c-st/cadvisor,mesosphere/cadvisor,derekwaynecarr/cadvisor,mesosphere/cadvisor,f0/cadvisor,bpradipt/cadvisor,megamsys/cadvisor,CrazyJvm/cadvisor,linux-on-ibm-z/cadvisor,aivarasko/cadvisor,difro/cadvisor,guoshimin/cadvisor,c-st/cadvisor,erSitzt/cadvisor,f0/cadvisor,BrickXu/cadvisor,ncdc/cadvisor,derwolfe/cadvisor,ncdc/cadvisor,ncdc/cadvisor,timstclair/cadvisor,bowlofstew/cadvisor,hacpai/cadvisor,bpradipt/cadvisor,kmicheal/cadvisor,dalanlan/cadvisor,takecy/cadvisor,jimmidyson/cadvisor,hzy001/cadvisor,yifan-gu/cadvisor,yolkov/cadvisor,vegasbrianc/cadvisor,datawisesystems/cadvisor,bing6/cadvisor,shilpamayanna/cadvisor,BrickXu/cadvisor,atyenoria/cadvisor,ainsleyc/cadvisor,CrazyJvm/cadvisor,vishh/cadvisor,jmaitrehenry/cadvisor,mangalaman93/cadvisor,whosthatknocking/cadvisor,rajthilakmca/cadvisor,dchen1107/cadvisor,derwolfe/cadvisor,afein/cadvisor