removed proto encoding for most of the abci types

[pompon0]

Most abci types are not encoded anywhere, because sei nodes are monoliths.
Additionally:

• folded RequestPrepareProposal fields into a single Header field, similarly to RequestFinalizeBlock in the previous pr.
• removed some unused mocks

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Mar 20, 2026, 8:46 AM

[codecov]

Codecov Report

❌ Patch coverage is 5.06912% with 206 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.63%. Comparing base (843a717) to head (fc5faf1).
⚠️ Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-tendermint/abci/types/plain_types.go	1.48%	199 Missing ⚠️
sei-cosmos/baseapp/abci.go	33.33%	3 Missing and 1 partial ⚠️
sei-tendermint/libs/service/service.go	33.33%	1 Missing and 1 partial ⚠️
app/benchmark.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3087      +/-   ##
==========================================
- Coverage   58.71%   58.63%   -0.08%     
==========================================
  Files        2094     2093       -1     
  Lines      172972   173109     +137     
==========================================
- Hits       101563   101510      -53     
- Misses      62426    62616     +190     
  Partials     8983     8983              

Flag	Coverage Δ
sei-chain-pr	61.05% <5.06%> (?)
sei-db	70.41% <ø> (-0.22%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
sei-tendermint/internal/state/execution.go	79.38% <100.00%> (-0.58%)	⬇️
app/benchmark.go	44.82% <0.00%> (ø)
sei-tendermint/libs/service/service.go	73.21% <33.33%> (+1.54%)	⬆️
sei-cosmos/baseapp/abci.go	60.83% <33.33%> (-1.22%)	⬇️
sei-tendermint/abci/types/plain_types.go	6.14% <1.48%> (-22.43%)	⬇️

... and 21 files with indirect coverage changes

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