bring back most of the recoverWith changes

[pjfanning]

• aimed at 2.0.0 only - it doesn't seem worth the risk with breaking stuff on 1.x
• omits the failure handling that was added before as this seems to be what caused the http2 testing issues in pekko-http
• I have tested this with pekko-http locally
• see Revert recent changes to recoverWith #2674
• the original changes were by @He-Pin - I have just removed some parts that seemed to be problematic

[He-Pin]

thanks ,I was planning looking at it tomorrow, I will.check it in detail.

The problem is we don't have a test to cover the edge cases...

[pjfanning]

I'd prefer to add the changes back incrementally but any enhancement to the test cases is definitely a great start

[pjfanning]

#2712 covers this