[Feature] markLine label auto position

[da730]

What problem does this feature solve?

when markline.autoRange=true, label of the markline will be clipped:

the position of the label should be auto changed to avoid clip like this:

It will first use the position in label.position if it can be fully displayed.

What does the proposed API look like?

markline:{
autoRange:true,
label:{
autoPosition:true
}

}

[kkxxkk2019]

label 上配置 confine: true 即可