Feature request: alive-only random/round-robin strategy

[miladrahimi]

Our outbound connections sometimes get blocked unexpectedly. To keep this from affecting users, load balancers (random/round-robin) should automatically skip any blocked connections.

Seems there is a similar feature in v2ray:
v2fly/v2ray-core#2850

[Fangliding]

There is already such feature, but it doesn't seem to be written in the document (damn)

[chise0713]

I think the label should be documentation instead dependencies.

[yuhan6665]

I need to move the code and add to round robin..

[yuhan6665]

应该可以了 84eeb56
@miladrahimi please help test. On xray side, I didn't add extra config. You just need to add fallbackTag as well as burstObservatory, the feature should be on.