fix: allow overlapping types in Expected

[mvadari]

High Level Overview of Change

This PR allows Expected to have overlapping types.

Context of Change

I ran into an issue with Expected<std::uint32_t, Json::Value>, which wouldn't build because of implicit conversion from unsigned int to Json::Value. This fixed the issue.

Type of Change

• Bug fix (non-breaking change which fixes an issue)

API Impact

N/A

Test Plan

Added a test

[godexsoft]

Great job 🚀

[Bronek]

Nice unit test !

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.9%. Comparing base (ea1fffe) to head (56ebe54).
Report is 4 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #5218   +/-   ##
=======================================
  Coverage     77.9%   77.9%           
=======================================
  Files          783     783           
  Lines        66677   66707   +30     
  Branches      8108    8119   +11     
=======================================
+ Hits         51921   51953   +32     
+ Misses       14756   14754    -2     

Files with missing lines	Coverage Δ
include/xrpl/basics/Expected.h	100.0% <100.0%> (ø)

... and 7 files with indirect coverage changes

[mvadari]

This is ready to merge