[JS] Data Plane API View Excludes Customized Code

# Issue
Currently, js automation tool removes everything and generate SDKs to validate emitter codegen work or not. But the generated API view doesn't contain customize code, which makes generated API view is helpless

# Considerations
- Customized code modifies inline the generated code from js emitter
- Different folder structures on customized code (sdk, test and sample)

# Solutions
Still in discussion, and there are some options we can consider below

## Option 1
Generate on top of existing code first then remove it and regenerate if build errors happen

### Considerations
- How to make people be aware of the automation is built on top of customized code or not
- How to handle customized samples build failures

## Option 2
Generate on top of existing code only

### Considerations
- js emitter team cares about the codegen quality, but is unable to locate the changes in API view from codegen or customized code easily