bug: TestProtocol_FetchBucketAndValidate flaky in staking test suite

[raullenchai]

Description

TestProtocol_FetchBucketAndValidate fails intermittently when run as part of the full staking test suite (go test ./action/protocol/staking/) but passes consistently when run in isolation.

Reproduction

# Fails intermittently:
go test ./action/protocol/staking/ -count=1

# Always passes:
go test ./action/protocol/staking/ -run TestProtocol_FetchBucketAndValidate -v

Likely cause

Concurrent state DB access or shared test fixture race condition when other staking tests modify global state.

Observed on both macOS arm64 (M3 Pro, Go 1.26.1) and macOS arm64 (M3 Ultra, Go 1.24.6).