Create BUILD rules for validator.proto (#28696)
Create BUILD rules for validator.proto (#28696)

TODO. Will write build rules to generate validator.pb.go
yandex-pcode/amphtml,prateekbh/amphtml,jpettitt/amphtml,honeybadgerdontcare/amphtml,nexxtv/amphtml,smartadserver/amphtml,smartadserver/amphtml,zhouyx/amphtml,nexxtv/amphtml,alanorozco/amphtml,alanorozco/amphtml,zhouyx/amphtml,media-net/amphtml,voyagegroup/amphtml,yandex-pcode/amphtml,honeybadgerdontcare/amphtml,Gregable/amphtml,ampproject/amphtml,honeybadgerdontcare/amphtml,prateekbh/amphtml,nexxtv/amphtml,media-net/amphtml,yandex-pcode/amphtml,ampproject/amphtml,jridgewell/amphtml,adup-tech/amphtml,jridgewell/amphtml,jpettitt/amphtml,danielrozenberg/amphtml,sharethrough/amphtml,voyagegroup/amphtml,media-net/amphtml,adup-tech/amphtml,rsimha-amp/amphtml,voyagegroup/amphtml,media-net/amphtml,yandex-pcode/amphtml,adup-tech/amphtml,jridgewell/amphtml,jmadler/amphtml,honeybadgerdontcare/amphtml,danielrozenberg/amphtml,adup-tech/amphtml,jmadler/amphtml,rsimha-amp/amphtml,sharethrough/amphtml,jridgewell/amphtml,sharethrough/amphtml,mhc-gh/amphtml,nexxtv/amphtml,Gregable/amphtml,ampproject/amphtml,smartadserver/amphtml,jmadler/amphtml,lannka/amphtml,lannka/amphtml,ampproject/amphtml,prateekbh/amphtml,prateekbh/amphtml,lannka/amphtml,ampproject/amphtml,jmadler/amphtml,mhc-gh/amphtml,Gregable/amphtml,sharethrough/amphtml,honeybadgerdontcare/amphtml,media-net/amphtml,danielrozenberg/amphtml,rsimha-amp/amphtml,smartadserver/amphtml,ampproject/amphtml,jpettitt/amphtml,nexxtv/amphtml,media-net/amphtml,prateekbh/amphtml,zhouyx/amphtml,nexxtv/amphtml,rsimha-amp/amphtml,Gregable/amphtml,danielrozenberg/amphtml,jmadler/amphtml,jpettitt/amphtml,media-net/amphtml,adup-tech/amphtml,mhc-gh/amphtml,honeybadgerdontcare/amphtml,zhouyx/amphtml,lannka/amphtml,danielrozenberg/amphtml,alanorozco/amphtml,rsimha-amp/amphtml,alanorozco/amphtml,voyagegroup/amphtml,lannka/amphtml,lannka/amphtml,alanorozco/amphtml,alanorozco/amphtml,jridgewell/amphtml,nexxtv/amphtml,mhc-gh/amphtml,zhouyx/amphtml,mhc-gh/amphtml,ampproject/amphtml,jpettitt/amphtml,mhc-gh/amphtml,danielrozenberg/amphtml,Gregable/amphtml,voyagegroup/amphtml,prateekbh/amphtml,mhc-gh/amphtml,media-net/amphtml,alanorozco/amphtml,smartadserver/amphtml,zhouyx/amphtml,jridgewell/amphtml,mhc-gh/amphtml,adup-tech/amphtml,rsimha-amp/amphtml,Gregable/amphtml,danielrozenberg/amphtml,yandex-pcode/amphtml,jpettitt/amphtml,yandex-pcode/amphtml,smartadserver/amphtml,zhouyx/amphtml,danielrozenberg/amphtml,Gregable/amphtml,sharethrough/amphtml,jridgewell/amphtml,lannka/amphtml,voyagegroup/amphtml,sharethrough/amphtml,prateekbh/amphtml,jmadler/amphtml,yandex-pcode/amphtml,voyagegroup/amphtml,ampproject/amphtml,Gregable/amphtml,alanorozco/amphtml,honeybadgerdontcare/amphtml,jpettitt/amphtml,rsimha-amp/amphtml,jpettitt/amphtml