feat: add linode SD failure count metric (#10673)
feat: add linode SD failure count metric (#10673)

This commit introduces a new metric to count the number of failed
requests to Linode's API when using Linode SD. Resolves #10672, inspired
by #10476.

_Note_: this doens't count failures when polling the `/account/events`
endpoint, as a `401` there is how we determine if the supplied token has
the needed API scopes to do event polling vs full refreshes each
interval.

Signed-off-by: TJ Hoplock <7f3395e84586ef27e4f0e696a65757ff645ab13a@gmail.com>
prometheus/prometheus,prometheus/prometheus,prometheus/prometheus,prometheus/prometheus,prometheus/prometheus