Improve upgradeable examples folder structure, explain differences

[cmichi]

Failure of the ink-waterfall CI stage is expected, since the paths have not yet been adapted there.

[codecov-commenter]

Codecov Report

Merging #1188 (76d9d53) into master (a35e159) will decrease coverage by 17.22%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master    #1188       +/-   ##
===========================================
- Coverage   78.98%   61.76%   -17.23%     
===========================================
  Files         229      228        -1     
  Lines        8667     8637       -30     
===========================================
- Hits         6846     5335     -1511     
- Misses       1821     3302     +1481     

Impacted Files	Coverage Δ
crates/lang/codegen/src/traits.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/ir/src/ir/contract.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/codegen/src/generator/env.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/codegen/src/generator/mod.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/codegen/src/enforced_error.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/codegen/src/generator/blake2b.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/codegen/src/generator/storage.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/codegen/src/generator/arg_list.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/codegen/src/generator/contract.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/codegen/src/generator/selector.rs	0.00% <0.00%> (-100.00%)	⬇️
... and 51 more

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