product: Consider using logger and capture stdout/stderr in GetVersion

Currently getting product version may fail in some rare cases and while we would report this as an error, we don't explicitly capture the stdout or stderr to make debugging of such problems easier.

https://github.com/hashicorp/hc-install/blob/7e86c538be9d48d3ff55df4553b39b1527d08664/product/terraform.go#L29-L49

See also https://github.com/hashicorp/terraform-plugin-sdk/issues/823

Start with product/terraform.go at lines 29-49 and review how GetVersion currently reports failures. Check the related Terraform plugin SDK issue for context, then trace the existing logging and command-output handling. Done means version lookup failures preserve useful stdout/stderr diagnostics and use the project’s logger.

Written by the indexing model from the issue text.