test(e2e): enhance and fix test of svg example

[CodinCat]

Currently the failing test is expected

I found a bug that is probably caused by v-model. I tried but I could't fix it so I add test to cover this issue (the new assertStats part). Therefore the test of this PR should fail now. I can rebase and push after it's fixed.

To reproduce the issue:

1. Open the svg example
2. Remove the first range control A
3. Drag other ranges, they are now broken

For now it can be fixed by adding key, but in Vue 2.0 key is not required. (If it is required in Vue 3.0, I can help with fixing the example in this PR)
I also add the assertLabels which can catch the issue of #552 for regression.

The same SVG example in Vue 2.0 passes all the newly added tests.

Changes:

• Rename setValue to more accurate typeValue
• Add setValue which will set value and dispatch input event
• Add assertLabels test
• Fix the broken assertStats. It didn't assert anything, sorry for my stupid mistake...
• Rename assertStats to assertPolygon because there is a new assertStats