[4.4.34] HTTP client thread-safety and CI infrastructure updates

- Improved concurrency safety by replacing the global HTTP client with a thread-safe, lazy-initialized instance using `sync.Once`. The new implementation enables connection pooling (`MaxIdleConnsPerHost`, connections per host) and dynamically configures pool size based on `obidefault.ParallelWorkers()`, ensuring robust behavior in multi-threaded Lua environments.
- Updated GitHub Actions workflows to the latest stable versions of `actions/setup-go` and ` actions/checkout`, improving build reliability.
- Removed outdated Go dependency checksums for buger/jsonparser v1.1.x to keep the build clean and consistent.

version.txt

@@ -1 +1 @@
-4.4.33
+4.4.34