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

physical/mssql/mssql_test.go

@@ -4,9 +4,9 @@ import (
 	"os"
 	"testing"
 
-	"github.com/hashicorp/vault/helper/logformat"
+	log "github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/vault/helper/logging"
 	"github.com/hashicorp/vault/physical"
-	log "github.com/mgutz/logxi/v1"
 
 	_ "github.com/denisenkom/go-mssqldb"
 )
@@ -31,7 +31,7 @@ func TestMSSQLBackend(t *testing.T) {
 	password := os.Getenv("MSSQL_PASSWORD")
 
 	// Run vault tests
-	logger := logformat.NewVaultLogger(log.LevelTrace)
+	logger := logging.NewVaultLogger(log.Debug)
 
 	b, err := NewMSSQLBackend(map[string]string{
 		"server":   server,