Migrate golangci-lint to v2

[Okabe-Junya]

What

Update the following tools related to golangci-lint:

• Update golangci-lint to v2.4.0 (for Go 1.25 support)
• Update reviewdog/action-golangci-lint to v2.8.0 (for golangci-lint v2 support)

Why

Bumping Go 1.25 is required these migrations

Reference

• Migration guide - Golangci-lint
• reviewdog/action-golangci-lint@v2.8.0
• golangci/golangci-lint@v2.4.0

Originally posted by @Warashi in #6128 (comment)