EmbeddedStoragePersistServiceImpl and ExternalStoragePaginationHelperImpl use “+=” to concatenated String, will cause performance issue

[showkawa]

Issue Description

bug report - performance issue

Describe what happened (or what feature you want)

com.alibaba.nacos.config.server.service.repository.EmbeddedStoragePersistServiceImpl
and
com.alibaba.nacos.config.server.service.repository.ExternalStoragePaginationHelperImpl
use “+=” to concatenated String, will cause performance issue

Describe what you expected to happen

use StringBuilder will be better, and i will handle it

How to reproduce it (as minimally and precisely as possible)

1. replace "+=" to StringBuilder append method

Tell us your environment

Anything else we need to know?

[showkawa]

@i will solve it@

[chuntaojun]

Simplify the label of issue