Retry BcContainerHelper downloads (#2292)

Intermittent network errors while downloading BcContainerHelper from
blob storage can fail AL-Go actions before the helper is imported. This
wraps the existing BcContainerHelper ZIP downloads in the shared retry
helper so transient request failures get another chance before the
action fails or falls back from a developer URL to preview.

The change keeps the existing download sources and version selection
behavior unchanged; it only adds retry behavior around the existing
`DownloadFile()` calls.

Co-authored-by: aholstrup1 <aholstrup1@users.noreply.github.com>