Invoice: Improve events display (#5775)

Closes #5773.

- Adds seconds to the displayed date and time
- Adds a tooltip that displays the full date and time including milliseconds
- Reintroduced the colored text in case of unusual events/states (this didn't work before)

BTCPayServer.Data/Data/InvoiceEventData.cs

@@ -40,7 +40,6 @@ namespace BTCPayServer.Data
         {
             return Severity switch
             {
-                EventSeverity.Info => "info",
                 EventSeverity.Error => "danger",
                 EventSeverity.Success => "success",
                 EventSeverity.Warning => "warning",