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/generic-handlers_test.go

@@ -113,7 +113,7 @@ func TestGuessIsRPC(t *testing.T) {
 
 // Tests browser request guess function.
 func TestGuessIsBrowser(t *testing.T) {
-	globalIsBrowserEnabled = true
+	globalBrowserEnabled = true
 	if guessIsBrowserReq(nil) {
 		t.Fatal("Unexpected return for nil request")
 	}