Create 10-day lock up on REX unstaking

[karynemayer]

Overview

A governance amendment was passed that requires this to be implemented. This aligns REX with sTLOS.

Acceptance criteria

• An escrow contract with behavior similar to sTLOS escrow that would lock up the TLOS for a specified number of days
• REX will specify the number of days (10, in this case)
• REX contract modified, so it sends to the escrow on withdrawal instead of sending it back to the user
• Remove initial four-day lock, if scope is reasonable

Technical considerations

Tasks

• [x] Write the SC @poplexity
• [ ] Review the code @guilledk @aamirpashaa @tomtomcrypto @donnyquixotic

[poplexity]

I have put an MVP together for the escrow contract here