Chore: Basic retry support for HTTP fetch on PromiseRelease

[abangser]

The current implementation is a single HTTP request (

kratix/lib/fetchers/url.go

Line 17 in 0314320

resp, err := http.Get(urlString)

). This is something that will work a lot of the time, but not all of the time. Some basic resiliency issues such as network blips should be handled by Kratix by default.

Add a simple retry mechanism with sensible backoffs/timeouts. Possibly leveraging this library.