Add background upload configuration info to batch deleted telemetry

[maciejburda]

What and why?

Enriches Batch Deleted telemetry metric with backgroundTaskEnabled configuration info. This is needed for measuring batch delivery success rate based on existence of the configuration.

How?

I have found unused field in_background which was hardcoded to false, and passed the configuration value to it.

Now, we might consider following:

• Use in_background for it's original purpose (although this is slightly harder task, because we need to determine the app state when deleting the file).
• Pass configuration value to a different property (i.e. is_bg_task_enabled)

Although after some deliberation I realized that we're mostly interested in measuring the difference is success rate for two different configurations, rather than knowing if batch file was deleted in background/foreground.

Looking for some feedback on that 🙌

Review checklist

• [x] Feature or bugfix MUST have appropriate tests (unit, integration)
• [ ] Make sure each commit and the PR mention the Issue number or JIRA reference
• [ ] Add CHANGELOG entry for user facing changes

[datadog-datadog-prod-us1[bot]]

Datadog Report

Branch report: maciey/add-backgroundtask-telemetry Commit report: 2510312 Test service: dd-sdk-ios

:white_check_mark: 0 Failed, 1869 Passed, 0 Skipped, 1m 14.71s Total Time :arrow_up: Test Sessions change in coverage: 3 increased, 5 no change