Recreating v1.9.1

Update SDK in go.mod for 1.8.6 (hashicorp#13307)

Go get and go mod vendor for 1.7.7 (hashicorp#13306)

Revert more downgrades from hashicorp#12975. (hashicorp#13168) (hashi…

…corp#13172)

GCP and Azure Login methods for Go client library (hashicorp#13022)

* Add native Login method for GCP auth backend

* Add native Login method for Azure auth backend

* Add changelog entry

* Use official azure library Environment struct rather than passing string, add timeouts

* Use v1.3.0 which now has interface definition

* Don't throw away error and close resp body

* Back to WithResource so we can support non-Azure URLs for aud

GCP and Azure Login methods for Go client library (hashicorp#13022)

* Add native Login method for GCP auth backend

* Add native Login method for Azure auth backend

* Add changelog entry

* Use official azure library Environment struct rather than passing string, add timeouts

* Use v1.3.0 which now has interface definition

* Don't throw away error and close resp body

* Back to WithResource so we can support non-Azure URLs for aud

Remove reference to local api module, use v1.3.0 (hashicorp#13105)

Remove reference to local api module, use v1.3.0 (hashicorp#13105)

Remove reference to local api module, use v1.3.0 (hashicorp#13105)

Remove reference to local api module, use v1.3.0 (hashicorp#13105)