[Doc] optimize the FE config document

[zy-kkk]

Search before asking

• I had searched in the issues and found no similar issues.

Description

I find that there are too many FE configuration items and it is difficult to find them. I think we should optimize the structure of the configuration item document

Solution

I summarized several categories of configuration items and sorted all configuration items neatly
1、Metadata & Cluster
2、Service
3、Query engine
4、Load & Export
5、Log
6、Storage
7、External table
8、External Resources
9、Else

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct