feat: basefee caculation for fip0115

[LinZexiao]

关联的Issues (Related Issues)

ref #6525

改动 (Proposed Changes)

• add ComputeNextBaseFeeFromPremiums

附注 (Additional Info)

自查清单 (Checklist)

在你认为本 PR 满足被审阅的标准之前，需要确保 / Before you mark the PR ready for review, please make sure that:

• 符合Venus项目管理规范中关于PR的相关标准 / The PR follows the PR standards set out in the Venus project management guidelines
• 具有清晰明确的commit message / All commits have a clear commit message.
• 包含相关的的测试用例或者不需要新增测试用例 / This PR has tests for new functionality or change in behaviour or not need to add new tests.
• 存在兼容性问题（接口, 配置，数据，灰度），如果存在需要进行文档说明 / This PR has compatibility issues (API, Configuration, Data, GrayRelease), if so, need to be documented.
• 包含相关的的指南以及文档或者不需要新增文档 / This PR has updated usage guidelines and documentation or not need
• 通过必要的检查项 / All checks are green

[Copilot]

Pull request overview

Implements the FIP-0115 base fee update path by deriving the next base fee from message gas premiums (rather than utilization), and updates effective gas premium calculation to clamp negative rewards to zero.

Changes:

• Add premium-based base fee computation (ComputeNextBaseFeeFromPremiums) and supporting weighted percentile selection logic.
• Clamp EffectiveGasPremium to never return a negative value when GasFeeCap < BaseFee.
• Add/adjust tests covering EffectiveGasPremium, weighted selection, and next-base-fee-from-premium formula.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
venus-shared/actors/types/message.go	Clamp effective gas premium to zero when GasFeeCap is below BaseFee.
venus-shared/actors/types/message_test.go	New unit tests for EffectiveGasPremium edge cases.
pkg/chain/message_store.go	Add premium-based base fee computation + weighted quickselect percentile helper.
pkg/chain/message_store_test.go	Add tests for weighted quickselect determinism and next-base-fee-from-premium formula.
pkg/chain/export_test.go	Expose internal helpers for testing.
pkg/constants/chain_parameters.go	Add BlockGasTargetIndex constant for percentile selection.
pkg/config/config.go	Add new fork upgrade height field (currently placeholder-named) and minor comment formatting.
app/submodule/eth/eth_test.go	Update reward expectation to match clamped premium behavior.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 59.30233% with 35 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (feat/nv28@4efd8a5). Learn more about missing BASE report.

Additional details and impacted files

@@             Coverage Diff             @@
##             feat/nv28   #6528   +/-   ##
===========================================
  Coverage             ?     22%           
===========================================
  Files                ?     790           
  Lines                ?   83671           
  Branches             ?       0           
===========================================
  Hits                 ?   18426           
  Misses               ?   62372           
  Partials             ?    2873           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[LinZexiao]

@wjmelements Would you mind reviewing this pr, please?

[wjmelements]

base fee adjustment, activation, and tests look good to me

[y-ang2010]

lgtm