Update Index configuration

[josecelano]

The Torrust Index config file has been updated, and some API endpoints exposing the configuration have also changed. We must apply those changes here.

• [x] Update config files
• [x] https://github.com/torrust/torrust-index-types-lib/issues/20 (Update types lib)
• [x] Update code referencing changes in the API response

Old version

[logging]
log_level = "info"

[tracker]
mode = "public"

New version

version = "2"

[logging]
threshold = "info"

[tracker]
private = false
listed = false

[josecelano]

ACK 59a87c77f65f52f1cdf11c84f0df9bf25f7b9ab4