[grafana] Improve dashboards download script

[xinity]

This PR aims at improving the logging experience of the dowload dashboards script to :

• avoid leaking git token in the execution logs
• add more information about which download is downloaded from wich source
• output the curl error message if any

[jkroepke]

Please bump the chart version, thanks!

[xinity]

@jkroepke oups, missed this, done :)

[jkroepke]

please fix CI failures and MR conflicts

[xinity]

@jkroepke will squash to improve readability

[zanhsieh]

@xinity Please bump the chart version and sign DCO. Thank you.

[xinity]

@zanhsieh too many commits but signed and fix :)