[giga] add executor interfaces for VM

[codchen]

Describe your changes and provide context

EVM implementations roughly adopt the following paradigm:

some preprocessing
calls the VM
- the VM starts doing stuff internally
some postprocessing

This PR defines the interfaces for the calls the VM part. The goal is so that we can relatively easily swap out the VM without changes to the rest of the codebase.
It also defines the storage interface for preprocessing/postprocessing to use without worrying about the underlying storage implementation (which is VM-specific).

The PR also provides implementation of the interfaces by Geth and EVMC, but not storage interface implementation yet.

Testing performed to validate your change

no functional changes.

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Dec 22, 2025, 3:44 AM

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Dec 15, 2025, 9:40 AM

[codecov]

Codecov Report

❌ Patch coverage is 0% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 43.70%. Comparing base (531d17d) to head (0bd1bc9).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
giga/executor/vm/evmc/vm.go	0.00%	12 Missing ⚠️
giga/executor/vm/geth/vm.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2601      +/-   ##
==========================================
- Coverage   43.70%   43.70%   -0.01%     
==========================================
  Files        1899     1901       +2     
  Lines      158894   158914      +20     
==========================================
+ Hits        69449    69457       +8     
- Misses      83039    83050      +11     
- Partials     6406     6407       +1     

Flag	Coverage Δ
sei-chain	45.70% <0.00%> (+<0.01%)	⬆️
sei-cosmos	38.03% <ø> (ø)
sei-db	69.06% <ø> (ø)
sei-tendermint	47.48% <ø> (-0.03%)	⬇️

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

Files with missing lines	Coverage Δ
giga/executor/vm/geth/vm.go	0.00% <0.00%> (ø)
giga/executor/vm/evmc/vm.go	0.00% <0.00%> (ø)

... and 19 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.