[FLINK-6667] Pass a callback type to the RestartStrategy, rather than the full ExecutionGraph

[FangYongs]

… the full ExecutionGraph

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[FangYongs]

@StephanEwen @tillrohrmann As discussed in #4220, I create this PR to fix issue FLINK-6667. Could you please have a look when you're free, thanks :)

[StephanEwen]

@zjureel Thanks for this patch. I will pick it up from here.
I think there is a small additional change needed, and a test, but I can do that...

[FangYongs]

Thank you for your reply, I will fix FLINK-6665 after this PR is merged, thanks :)

[StephanEwen]

I have taken and adapted the code for the patch in #4364

[StephanEwen]

Thank you for the contribution!
The code form this PR has been improved and merged in this commit: 65400bd

If you agree, could you close this PR?

[FangYongs]

Thank you for your merging, thanks