meta: adjustment for builtin plugin directories

[rickycao-qy]

This PR includes:

• move plugins-related folder into subfolder 'plugins'
• remove prefix 'pipcook-plugins' for plugin folders
• fix tjs-node-gpu verison

@yorkie Please have a review please

[yorkie]

And how about creating a shared tsconfig.json for all built-in plugins?

[rickycao-qy]

And how about creating a shared tsconfig.json for all built-in plugins?

For lerna practise, I follow some guides online. I guess it's recommended to create separate tsconfig for each package and extends a common tsconfig since package should be regarded as independent pacakge? How do you think

[yorkie]

Thanks for the guideline link, and how about tweaking our tsconfig inheritance as the following:

(tsconfig for independent plugin)
-------------------------------
tsconfig for common plugin
-------------------------------
tsconfig for root

And there are some notes for the above:

• independent plugin configuration is optional, but "extend" is required.
• common plugin config could be also used for our non-official plugin developer in the future.