config: Reorganize defs/params and make them configurable

[jiping-s]

Background

defs/params.go contains advanced parameters. Some of the values are shared while others are specific to certain packages or individual modules. Some of them also have dependencies on others and cannot be set to any arbitrary values.

What to do

• Move parameters to corresponding packages or individual units and add them to configuration
• For parameters that have inter-dependencies, either calculate the values automatically or check the values when loading config