Migrate config to KV data format (#8392)

- adding oauth support to MinIO browser (#8400) by @kanagaraj
- supports multi-line get/set/del for all config fields
- add support for comments, allow toggle
- add extensive validation of config before saving
- support MinIO browser to support proper claims, using STS tokens
- env support for all config parameters, legacy envs are also
  supported with all documentation now pointing to latest ENVs
- preserve accessKey/secretKey from FS mode setups
- add history support implements three APIs
  - ClearHistory
  - RestoreHistory
  - ListHistory
- add help command support for each config parameters
- all the bug fixes after migration to KV, and other bug
  fixes encountered during testing.

cmd/gateway-startup-msg.go

@@ -52,7 +52,7 @@ func printGatewayStartupMessage(apiEndPoints []string, backendType string) {
 // Prints common server startup message. Prints credential, region and browser access.
 func printGatewayCommonMsg(apiEndpoints []string) {
 	// Get saved credentials.
-	cred := globalServerConfig.GetCredential()
+	cred := globalActiveCred
 
 	apiEndpointStr := strings.Join(apiEndpoints, "  ")
 
@@ -64,7 +64,7 @@ func printGatewayCommonMsg(apiEndpoints []string) {
 	}
 	printEventNotifiers()
 
-	if globalIsBrowserEnabled {
+	if globalBrowserEnabled {
 		logStartupMessage(color.Blue("\nBrowser Access:"))
 		logStartupMessage(fmt.Sprintf(getFormatStr(len(apiEndpointStr), 3), apiEndpointStr))
 	}