Update the implementations of the helm repository downloaders to return
implementation specific typed error from GetChartVersion(). This is
needed to distinguish between persistent build error and transient build
error.
In the case of OCI charts, a transient network failure shouldn't be
considered a persistent build failure of the chart and should be
retried.
Two repository errors, ErrReference and ErrExternal are introduced for
the repository downloader implementations to provide enough context
about the failure which can be used by the caller to add appropriate
context as per the needs. In case of chart builder, it adds the build
error context based on the repository error value.
Signed-off-by: Sunny <darkowlzz@protonmail.com>
Sunny