Allow setting of default_scrape_timeout

[boniek83]

I want to be able to set default_scrape_timeout to avoid errors like this:
ts=2024-08-07T23:37:29.89731873Z level=error msg="error generating scrapeconfig from serviceMonitor" component_path=/ component_id=prometheus.operator.servicemonitors.service_monitors name=rdc err="scrape timeout greater than scrape interval for scrape config with job name \"serviceMonitor/amdgpu/rdc/0\""
This particular error message is about prometheus operator objects but this setting should be applied to all scrape targets.
Example of scrape target I want to achieve:

      prometheus.operator.servicemonitors "all" {
        forward_to = [prometheus.remote_write.default.receiver]
        clustering {
          enabled  = true
        }
        scrape {
          default_scrape_interval = "30s"
          default_scrape_timeout  = "5s"
        }
      }