Revendor cortex to latest master

[sandeepsukhani]

What this PR does / why we need it:
There are some fixes in object client in Cortex which would be good to have for avoiding any problems running boltdb-shipper.
I have taken care of some of the changes done in Cortex, most important ones are at https://github.com/grafana/loki/blob/d580aa9da860d5bceee606cc5420c8eb20b275aa/pkg/querier/queryrange/queryrange.pb.patch.go

Checklist

• Tests updated

[codecov-io]

Codecov Report

Merging #2794 into master will decrease coverage by 0.07%.
The diff coverage is 36.84%.

@@            Coverage Diff             @@
##           master    #2794      +/-   ##
==========================================
- Coverage   61.39%   61.32%   -0.08%     
==========================================
  Files         177      178       +1     
  Lines       14394    14419      +25     
==========================================
+ Hits         8837     8842       +5     
- Misses       4748     4763      +15     
- Partials      809      814       +5     

Impacted Files	Coverage Δ
pkg/distributor/http.go	0.00% <0.00%> (ø)
pkg/loki/loki.go	0.00% <ø> (ø)
pkg/loki/modules.go	3.61% <0.00%> (-0.02%)	⬇️
pkg/querier/queryrange/queryrange.pb.patch.go	41.17% <41.17%> (ø)
pkg/querier/queryrange/codec.go	87.88% <100.00%> (+0.22%)	⬆️
pkg/promtail/targets/file/filetarget.go	64.08% <0.00%> (-2.12%)	⬇️
pkg/storage/stores/shipper/uploads/table.go	68.66% <0.00%> (-1.85%)	⬇️
...kg/storage/stores/shipper/uploads/table_manager.go	65.78% <0.00%> (-1.76%)	⬇️
pkg/logql/evaluator.go	89.64% <0.00%> (-0.40%)	⬇️
... and 1 more

[owen-d]

lgtm. We've called these proto add-on methods extensions.go before (https://github.com/grafana/loki/blob/master/pkg/logproto/extensions.go) if you'd like to keep this consistent.

[sandeepsukhani]

lgtm. We've called these proto add-on methods extensions.go before (https://github.com/grafana/loki/blob/master/pkg/logproto/extensions.go) if you'd like to keep this consistent.

Sounds good. Renamed it.
Thanks for the review!