Consolidate bridging logic

[sisyphusSmiling]

Closes: #47
Stacked on: #46

Description

Consolidates redundant code between FlowEVMBridge and FlowEVMBridgeHandlers related to fungible token bridging. Also adds helper methods in FlowEVMBridgeUtils to simplify the logic in the core bridge contract. Comments were added to further enhance readability.

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For contributor use:

• Targeted PR against master 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 93.33333% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 84.90%. Comparing base (306640a) to head (ae75dff).

Files	Patch %	Lines
cadence/contracts/bridge/FlowEVMBridgeUtils.cdc	94.44%	3 Missing ⚠️
cadence/contracts/bridge/FlowEVMBridge.cdc	86.66%	2 Missing ⚠️

Additional details and impacted files

@@                     Coverage Diff                      @@
##           add-special-case-handler      #48      +/-   ##
============================================================
- Coverage                     85.47%   84.90%   -0.57%     
============================================================
  Files                            18       18              
  Lines                           819      828       +9     
============================================================
+ Hits                            700      703       +3     
- Misses                          119      125       +6     

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[joshuahannan]

Looks pretty good! Just a few small comments

[joshuahannan]

Feel free to merge this to add-special-case-handler once you've merged consolidate-bridging-logic to this and after I have approved #46