store profiling files in `temp-dir` instead of `/tmp`

[hihihuhu]

Feature Request

Is your feature request related to a problem? Please describe:

currently the profiling files are stored in /tmp folder https://github.com/pingcap/tidb-dashboard/blob/v2023.07.05.1/pkg/apiserver/profiling/pprof.go#L61, which is cleared when pod restarts

Describe the feature you'd like:

because there is a temp-dir config, it makes more sense to store profiling files in that path as well, which is already backed by ebs in tidb-operator

Describe alternatives you've considered:

mount an ebs for /tmp in tidb-operator

Teachability, Documentation, Adoption, Migration Strategy: