Fix cases of underflow in event of storage decrease

[sisyphusSmiling]

Closes: #127

Description

• Guards against instances where escrowing an asset actually decreases account storage usage due to underlying storage implementation. This may be an instance where storage blocks are reshuffled such that to total stored object is more compact and thus consumes less storage than the object preceding the newly stored asset.

---

For contributor use:

• Targeted PR against main branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the standards mentioned here.
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 86.76%. Comparing base (02aab3f) to head (ebdcec4).
Report is 148 commits behind head on main.

Files with missing lines	Patch %	Lines
...adence/contracts/bridge/FlowEVMBridgeNFTEscrow.cdc	66.66%	1 Missing ⚠️
...ence/contracts/bridge/FlowEVMBridgeTokenEscrow.cdc	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #129      +/-   ##
==========================================
+ Coverage   86.19%   86.76%   +0.56%     
==========================================
  Files          18       18              
  Lines         884      967      +83     
==========================================
+ Hits          762      839      +77     
- Misses        122      128       +6     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[sisyphusSmiling]

Contracts updated

Testnet:
FlowEVMBridgeNFTEscrow - 3ca01bddff40c801a85722b4c26398f494a8ddd21064d21f368ab7ca564314b9
FlowEVMBridgeTokenEscrow - 7ee7a3e0ef9a9098787401cb57f185419eee5498a9af63832820b7bc63341611

Mainnet:
FlowEVMBridgeNFTEscrow - bcf0ff03db27f12a89dc61eeaaf839cfac0b9f55f1d2d808af423c7c17e438ad
FlowEVMBridgeTokenEscrow - e8cf480d5d974906f559d298e832cf346cce90ec724b89d4412b1f78df991449