fix: staking optimization v1.5.x patch

[randy-cro]

Description

This patch introduces a fixed gas consumption decorator in the antehandler to standardize gas usage for whitelisted messages.
Currently, only staking-related messages are included in the whitelist.

⚠️ Version Note:
As this is a v1.5 patch, all staking-related operations will be rejected at the antehandler level.
This serves as a warning for node operators about potential AppHash mismatches if inconsistent gas consumption is detected.

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Purpose

This ensures consistent gas consumption across all nodes, regardless of variations in staking cache size.
By normalizing gas usage, it prevents potential AppHash mismatches caused by node-specific performance differences.

Implementation Details

• A fixed gas amount is assigned per whitelisted message type.
• The values are derived from the average gas usage observed on mainnet.

For example, the mean gas used for MsgUndelegate can be referenced here:
Mainnet reference

This change works in tandem with the staking cache introduced in the Cosmos SDK:
crypto-org-chain/cosmos-sdk#1733

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For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

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For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
• Reviewers assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	golang/​github.com/​randy-cro/​cosmos-sdk@​v0.0.0-20251113072857-fbecd698368d

View full report

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 46.88%. Comparing base (1544264) to head (9220f2d).

Additional details and impacted files

@@                 Coverage Diff                 @@
##           release/v0.22.x     #779      +/-   ##
===================================================
+ Coverage            46.75%   46.88%   +0.12%     
===================================================
  Files                  187      188       +1     
  Lines                15221    15257      +36     
===================================================
+ Hits                  7117     7153      +36     
  Misses                7316     7316              
  Partials               788      788              

Files with missing lines	Coverage Δ
ante/cosmos/fixed_gas.go	100.00% <100.00%> (ø)
evmd/ante/evm_handler.go	100.00% <100.00%> (ø)
evmd/ante/handler_options.go	61.05% <100.00%> (+0.41%)	⬆️
evmd/app.go	78.64% <100.00%> (+0.23%)	⬆️

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