Refactor WASM host references

[sug0]

Describe your changes

Refactor WASM host references code.

Indicate on which release or other PRs this topic is based on

#3258

Diff for review: https://github.com/anoma/namada/compare/tiago/dont-export-wasm-mem..tiago/host-ref-refactor

Checklist before merging to draft

• I have added a changelog
• Git history is in acceptable state

[codecov]

Codecov Report

Attention: Patch coverage is 91.73554% with 10 lines in your changes are missing coverage. Please review.

Project coverage is 60.23%. Comparing base (4ed6229) to head (f7b9729).

Files	Patch %	Lines
crates/namada/src/vm/host_env.rs	92.04%	7 Missing ⚠️
crates/namada/src/vm/mod.rs	78.57%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3273      +/-   ##
==========================================
- Coverage   60.24%   60.23%   -0.02%     
==========================================
  Files         303      303              
  Lines       93191    93150      -41     
==========================================
- Hits        56145    56106      -39     
+ Misses      37046    37044       -2     

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[tzemanovic]

nice refactor!