Add test for escrow withdrawETH

[rkolpakov]

Test shows holder perspective of withdrawing unstETH in RQ state

[Psirex]

Good showcase of withdrawal handling and the peculiarities of the getVetoerDetails() method! 👍🏻 Left a comment with a suggestion to improve the test’s clarity

[sandstone-ag]

Thank you for the test - it covers an unobvious case. I suggest spending some effort into making the test easy to understand, for example, changing the naming of several variables and hiding complex parts in a helper methods.