modernize golog: remove vendor, dep, ginkgo; add go modules and github actions

[doron-sincere]

Summary

• Remove checked-in vendor directory (786K lines of vendored ginkgo/gomega)
• Replace dep (Gopkg.toml/Gopkg.lock) with Go modules (go 1.18, zero external deps)
• Replace CircleCI with GitHub Actions test workflow
• Migrate all tests from ginkgo/gomega to stdlib testing
• Replace interface{} with any throughout production code
• Fix doc comments and typos

Context

Part of the Go test modernization effort across Timehop repos. Migrating golog (a leaf dependency) removes the transitive ginkgo/gomega indirect deps from all downstream repos.

Test plan

• All 63 tests pass locally with go test -v -race ./...
• No ginkgo/gomega imports remain
• Zero external dependencies in go.mod
• GitHub Actions workflow runs on PR