Fix all possible setting error related storages and added some tests (#23911)

Follow up #22405

Fix #20703 

This PR rewrites storage configuration read sequences with some breaks
and tests. It becomes more strict than before and also fixed some
inherit problems.

- Move storage's MinioConfig struct into setting, so after the
configuration loading, the values will be stored into the struct but not
still on some section.
- All storages configurations should be stored on one section,
configuration items cannot be overrided by multiple sections. The
prioioty of configuration is `[attachment]` > `[storage.attachments]` |
`[storage.customized]` > `[storage]` > `default`
- For extra override configuration items, currently are `SERVE_DIRECT`,
`MINIO_BASE_PATH`, `MINIO_BUCKET`, which could be configured in another
section. The prioioty of the override configuration is `[attachment]` >
`[storage.attachments]` > `default`.
- Add more tests for storages configurations.
- Update the storage documentations.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/admin/config.tmpl

@@ -102,7 +102,7 @@
 				<dd>{{if .LFS.StartServer}}{{svg "octicon-check"}}{{else}}{{svg "octicon-x"}}{{end}}</dd>
 				{{if .LFS.StartServer}}
 					<dt>{{.locale.Tr "admin.config.lfs_content_path"}}</dt>
-					<dd>{{.LFS.Path}}</dd>
+					<dd>{{JsonUtils.EncodeToString .LFS.Storage.ToShadowCopy}}</dd>
 					<dt>{{.locale.Tr "admin.config.lfs_http_auth_expiry"}}</dt>
 					<dd>{{.LFS.HTTPAuthExpiry}}</dd>
 				{{end}}