decouple lg apis from editors (visual editor)

[yeze322]

currently, visual editor is invoking lg apis directly which causes unexpected http calls and potential redraws.

according to our previous work on extracting lg logic into lgutils and lgparser, decoupling lg logic will benefit us on editors' maintainability and improve overall engineering quality meanwhile reduce the migration cost when updating lg grammar version in composer.

based on the fact that lg lib itself is evolving outside the loop of composer and visualeditor, we need to inject lg apis in a more proper level. ideally, we can have a standalone module to map field value change to lg changes and finally triggers http calls. it could be shared accross visual and form.

[yeze322]

it's not completely done. one more pr required

[yeze322]

item finished. close it