chore: add two new upgrade examples + refactor existing ones

[moul]

Depends on #2342

cc @jeronimoalbi

[jeronimoalbi]

I really like the approach taken in upgrade_e and upgrade_f, they are elegant and idiomatic 👍

I'm wondering if it makes sense to eventually have another upgrade example case, where the "home" realm is actually versioned using v1, v2, and so on in the realm path for major versions, where the inner interface implementations from upgrade_e are considered minor versions. If this makes sense, it would allow "home" to eventually be bumped up to a new major version when any public realm functions or the interface changes.

[moul]

I'm wondering if it makes sense to eventually have another upgrade example case, where the "home" realm is actually versioned using v1, v2, and so on in the realm path for major versions, where the inner interface implementations from upgrade_e are considered minor versions. If this makes sense, it would allow "home" to eventually be bumped up to a new major version when any public realm functions or the interface changes.

To be tried!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.00%. Comparing base (b1c1c96) to head (85556b9).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2334      +/-   ##
==========================================
- Coverage   55.01%   55.00%   -0.01%     
==========================================
  Files         595      595              
  Lines       79765    79792      +27     
==========================================
+ Hits        43880    43890      +10     
- Misses      32567    32584      +17     
  Partials     3318     3318              

Flag	Coverage Δ
gno.land	64.15% <ø> (+0.01%)	⬆️

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