when i set dashboard_dir, i got a error: 'no such file or directory'

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

add dashboard_dir configuration
reload failed ,the error info is:
Error: init config failed: 172.31.18.208:3000: initial dashboards: read local directory /tidb-deploy/grafana-metrics/ failed: open /tidb-deploy/grafana-metrics/: no such file or directory

2. What did you expect to see?
   reload success

3. What did you see instead?
   reload failed，but metrics was changed when i flush grafana web

4. What version of TiUP are you using (tiup --version)?

[root@ip-172-31-31-118 conf]# tiup cluster --version
tiup is checking updates for component cluster ...
Starting component cluster: /root/.tiup/components/cluster/v1.11.1/tiup-cluster --version
tiup version 1.11.1 tiup
Go Version: go1.19.2
Git Ref: v1.11.1
GitHash: b95172df211e4f9b643590f2dd8436ad60c72b38
tiup --v[root@ip-172-31-31-118 conf]# tiup --version
1.11.1 tiup
Go Version: go1.19.2
Git Ref: v1.11.1
GitHash: b95172df211e4f9b643590f2dd8436ad60c72b38
[root@ip-172-31-31-118 conf]#

Start by locating the dashboard_dir configuration handling and the reload path that initializes local dashboards. Reproduce the failure with the reported directory configuration and TiUP cluster version, then verify that reload succeeds when the configured directory is handled correctly and existing metrics behavior remains intact.