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.

docs/sts/client-grants.md

@@ -93,25 +93,15 @@ http://minio.cluster:9000?Action=AssumeRoleWithClientGrants&DurationSeconds=3600
 ```
 $ export MINIO_ACCESS_KEY=minio
 $ export MINIO_SECRET_KEY=minio123
-$ export MINIO_IAM_JWKS_URL=https://localhost:9443/oauth2/jwks
-$ export MINIO_IAM_OPA_URL=http://localhost:8181/v1/data/httpapi/authz
+$ export MINIO_IDENTITY_OPENID_CONFIG_URL=https://localhost:9443/oauth2/oidcdiscovery/.well-known/openid-configuration
+$ export MINIO_POLICY_OPA_URL=http://localhost:8181/v1/data/httpapi/authz
 $ minio server /mnt/export
 
-$ mc admin config get myminio
-...
-{
-  "openid": {
-    "jwks": {
-      "url": "https://localhost:9443/oauth2/jwks"
-     }
-   }
-  "policy": {
-    "opa": {
-      "url": "http://localhost:8181/v1/data/httpapi/authz",
-      "authToken": ""
-    }
-  }
-}
+$ mc admin config get myminio identity_openid
+identity_openid config_url="https://localhost:9443/oauth2/oidcdiscovery/.well-known/openid-configuration" state="on"
+
+$ mc admin config get myminio policy_opa
+policy_opa auth_token="" state="on" url="http://localhost:8181/v1/data/httpapi/authz"
 ```
 
 Testing with an example