Move to "github.com/hashicorp/go-hclog" (#4227)

* logbridge with hclog and identical output

* Initial search & replace

This compiles, but there is a fair amount of TODO
and commented out code, especially around the
plugin logclient/logserver code.

* strip logbridge

* fix majority of tests

* update logxi aliases

* WIP fixing tests

* more test fixes

* Update test to hclog

* Fix format

* Rename hclog -> log

* WIP making hclog and logxi love each other

* update logger_test.go

* clean up merged comments

* Replace RawLogger interface with a Logger

* Add some logger names

* Replace Trace with Debug

* update builtin logical logging patterns

* Fix build errors

* More log updates

* update log approach in command and builtin

* More log updates

* update helper, http, and logical directories

* Update loggers

* Log updates

* Update logging

* Update logging

* Update logging

* Update logging

* update logging in physical

* prefixing and lowercase

* Update logging

* Move phyisical logging name to server command

* Fix som tests

* address jims feedback so far

* incorporate brians feedback so far

* strip comments

* move vault.go to logging package

* update Debug to Trace

* Update go-plugin deps

* Update logging based on review comments

* Updates from review

* Unvendor logxi

* Remove null_logger.go

command/command_test.go

@@ -9,6 +9,7 @@ import (
 	"testing"
 	"time"
 
+	log "github.com/hashicorp/go-hclog"
 	"github.com/hashicorp/vault/api"
 	"github.com/hashicorp/vault/audit"
 	"github.com/hashicorp/vault/builtin/logical/pki"
@@ -22,11 +23,10 @@ import (
 	auditFile "github.com/hashicorp/vault/builtin/audit/file"
 	credUserpass "github.com/hashicorp/vault/builtin/credential/userpass"
 	vaulthttp "github.com/hashicorp/vault/http"
-	logxi "github.com/mgutz/logxi/v1"
 )
 
 var (
-	defaultVaultLogger = logxi.NullLog
+	defaultVaultLogger = log.NewNullLogger()
 
 	defaultVaultCredentialBackends = map[string]logical.Factory{
 		"userpass": credUserpass.Factory,