Add rounding to Vault invariants

[Tapanito]

This PR relaxes Vault Deposit, Withdraw and Clawback invariants for IOUs to allow minimal discrepancy between various balance changes.

High Level Overview of Change

Context of Change

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov]

Codecov Report

❌ Patch coverage is 94.89051% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.8%. Comparing base (ed4330a) to head (d54a1f7).
⚠️ Report is 1 commits behind head on tapanito/lending-fix-amendment.

Files with missing lines	Patch %	Lines
src/libxrpl/tx/invariants/VaultInvariant.cpp	94.7%	7 Missing ⚠️

Additional details and impacted files

@@                      Coverage Diff                       @@
##           tapanito/lending-fix-amendment   #6217   +/-   ##
==============================================================
  Coverage                            79.8%   79.8%           
==============================================================
  Files                                 858     858           
  Lines                               67768   67847   +79     
  Branches                             7570    7554   -16     
==============================================================
+ Hits                                54064   54152   +88     
+ Misses                              13704   13695    -9     

Files with missing lines	Coverage Δ
include/xrpl/protocol/STAmount.h	95.7% <100.0%> (+0.1%)	⬆️
...clude/xrpl/tx/transactors/Lending/LendingHelpers.h	95.2% <100.0%> (ø)
...tx/transactors/Lending/LoanBrokerCoverWithdraw.cpp	96.3% <100.0%> (ø)
src/libxrpl/tx/invariants/VaultInvariant.cpp	97.4% <94.7%> (-0.8%)	⬇️

... and 10 files with indirect coverage changes

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[ximinez]

I created #6246 to make the some of the changes I requested below. Pretty much everything except the changes to the actual ValidVault invariant checks.

[Tapanito]

@ximinez apologies for the forced push, I haven't seen your review!

[Tapanito]

@ximinez as we discussed, I rewrote the Invariant to check relative distance between values within some tolerance. For IOU the tolerance is 1 * 10^-13, for MPT/XRP the tolerance is zero.

The IOU tolerance is the smallest tolerance that would cause the unit test to pass. If the tolerance was -14, the unit-test would fail.