fix: revert restricted balances

[dandanlen]

Pull Request

Closes: PRO-971

Checklist

Please conduct a thorough self-review before opening the PR.

• I am confident that the code works.
• I have updated documentation where appropriate.

Summary

This fixes two issues:

1. If, after withdrawing restricted funds, the account didn't have enough remaining funds to pay the tax, the redemption would fail due to 'insufficient unrestricted funds'. -> The solution is to reduce the restricted balance by the gross withdrawal amount, rather than the net redeemed amount. This means that when withdrawing to a restricted address, the tax is paid from the restricted balance.
2. If a withdrawal to a restricted address reverted, the restricted balance wasn't reverted (PRO-971) and the funds would thus lose their restriction. The solution was to store the amount and destination in the PendingRedemptions, and update the restricted balance if the redemption expires.

[linear]

PRO-971 Restrictions are lost if a redemption reverts

How to reproduce

Can the bug be reproduced? How? Ideally, provide a bouncer test or unit test that demonstrated the problem.

Redeem to a restricted address and let it expire.

Symptoms

How does the bug manifest? If it's not obvious, what behaviour did we expect?

The funds are credited back to the account but they are now unrestricted.

[dandanlen]

FYI @acdibble (thanks for raising this).

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (1de7247) 72% compared to head (a7f3a9e) 71%.
Report is 4 commits behind head on main.

Files	Patch %	Lines
state-chain/pallets/cf-funding/src/lib.rs	96%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #4237    +/-   ##
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- Coverage     72%     71%    -0%     
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  Files        384     384            
  Lines      63015   63180   +165     
  Branches   63015   63180   +165     
======================================
+ Hits       45074   45122    +48     
- Misses     15609   15723   +114     
- Partials    2332    2335     +3     

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