[AIRFLOW-2037] Add methods to get Hash values of a GCS object
[AIRFLOW-2037] Add methods to get Hash values of a GCS object

- Added `get_md5hash` and `get_crc32c` in
`gcs_hook` to aid in Data integrity validations.

Closes #2977 from kaxil/hashing_gcs_hook

jgao54/airflow,Fokko/incubator-airflow,fenglu-g/incubator-airflow,mistercrunch/airflow,bolkedebruin/airflow,owlabs/incubator-airflow,wolfier/incubator-airflow,sekikn/incubator-airflow,apache/incubator-airflow,DinoCow/airflow,spektom/incubator-airflow,r39132/airflow,nathanielvarona/airflow,yk5/incubator-airflow,mistercrunch/airflow,danielvdende/incubator-airflow,lxneng/incubator-airflow,airbnb/airflow,gtoonstra/airflow,sid88in/incubator-airflow,CloverHealth/airflow,owlabs/incubator-airflow,apache/airflow,adamhaney/airflow,jgao54/airflow,lyft/incubator-airflow,Fokko/incubator-airflow,apache/incubator-airflow,wileeam/airflow,sergiohgz/incubator-airflow,malmiron/incubator-airflow,cfei18/incubator-airflow,sekikn/incubator-airflow,wndhydrnt/airflow,apache/airflow,malmiron/incubator-airflow,wileeam/airflow,jgao54/airflow,adamhaney/airflow,spektom/incubator-airflow,Tagar/incubator-airflow,wooga/airflow,wolfier/incubator-airflow,artwr/airflow,fenglu-g/incubator-airflow,mtagle/airflow,wooga/airflow,nathanielvarona/airflow,jgao54/airflow,subodhchhabra/airflow,yk5/incubator-airflow,dhuang/incubator-airflow,subodhchhabra/airflow,DinoCow/airflow,sergiohgz/incubator-airflow,fenglu-g/incubator-airflow,akosel/incubator-airflow,sergiohgz/incubator-airflow,adamhaney/airflow,wileeam/airflow,DinoCow/airflow,apache/airflow,Tagar/incubator-airflow,wolfier/incubator-airflow,gtoonstra/airflow,mrkm4ntr/incubator-airflow,lyft/incubator-airflow,lxneng/incubator-airflow,criccomini/airflow,wileeam/airflow,Fokko/incubator-airflow,wndhydrnt/airflow,artwr/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,RealImpactAnalytics/airflow,RealImpactAnalytics/airflow,r39132/airflow,airbnb/airflow,apache/incubator-airflow,cfei18/incubator-airflow,lxneng/incubator-airflow,bolkedebruin/airflow,fenglu-g/incubator-airflow,airbnb/airflow,spektom/incubator-airflow,mtagle/airflow,wooga/airflow,owlabs/incubator-airflow,Acehaidrey/incubator-airflow,r39132/airflow,nathanielvarona/airflow,mtagle/airflow,cfei18/incubator-airflow,dhuang/incubator-airflow,Acehaidrey/incubator-airflow,artwr/airflow,malmiron/incubator-airflow,danielvdende/incubator-airflow,bolkedebruin/airflow,lxneng/incubator-airflow,mrkm4ntr/incubator-airflow,Tagar/incubator-airflow,lyft/incubator-airflow,andyxhadji/incubator-airflow,CloverHealth/airflow,bolkedebruin/airflow,yk5/incubator-airflow,apache/airflow,nathanielvarona/airflow,Tagar/incubator-airflow,mtagle/airflow,artwr/airflow,apache/airflow,criccomini/airflow,Acehaidrey/incubator-airflow,CloverHealth/airflow,sergiohgz/incubator-airflow,andyxhadji/incubator-airflow,andyxhadji/incubator-airflow,malmiron/incubator-airflow,r39132/airflow,akosel/incubator-airflow,Fokko/incubator-airflow,lyft/incubator-airflow,spektom/incubator-airflow,danielvdende/incubator-airflow,mrkm4ntr/incubator-airflow,sid88in/incubator-airflow,subodhchhabra/airflow,danielvdende/incubator-airflow,yk5/incubator-airflow,sid88in/incubator-airflow,owlabs/incubator-airflow,zack3241/incubator-airflow,wolfier/incubator-airflow,dhuang/incubator-airflow,edgarRd/incubator-airflow,nathanielvarona/airflow,RealImpactAnalytics/airflow,CloverHealth/airflow,airbnb/airflow,sekikn/incubator-airflow,wndhydrnt/airflow,cfei18/incubator-airflow,apache/airflow,edgarRd/incubator-airflow,cfei18/incubator-airflow,criccomini/airflow,DinoCow/airflow,edgarRd/incubator-airflow,dhuang/incubator-airflow,zack3241/incubator-airflow,wndhydrnt/airflow,bolkedebruin/airflow,criccomini/airflow,mistercrunch/airflow,Acehaidrey/incubator-airflow,wooga/airflow,mistercrunch/airflow,danielvdende/incubator-airflow,gtoonstra/airflow,RealImpactAnalytics/airflow,edgarRd/incubator-airflow,akosel/incubator-airflow,gtoonstra/airflow,zack3241/incubator-airflow,andyxhadji/incubator-airflow,mrkm4ntr/incubator-airflow,adamhaney/airflow,subodhchhabra/airflow,sid88in/incubator-airflow,danielvdende/incubator-airflow,sekikn/incubator-airflow,apache/incubator-airflow,Acehaidrey/incubator-airflow,akosel/incubator-airflow,zack3241/incubator-airflow