5.3.2
fix: remove used default zlevel
fix(graph): fix error when symbol is none.
fix(type): optimize types for dts bundling
style: using utility methods for type checking.
refact(data): separate List to DataStorage and SeriesData
refact: put all core modules in the core dir. only do export in lib/echarts
ts: let to const. And add eslint rule "prefer-const".
refact: use x, y, scaleX, scaleY instead of position and scale in Element
chore: reuse noop function from zrender util to reduce redundant code.
Merge branch 'master' into next-merge-master