[android] Add support for running workitems on specified Android emulator API levels

DNCENG team prepared a "multi" queue for Android API level testing which contains pre-installed emulators covering all API levels. We need to add support in xharness to be able to select on which emulators the workitems should run. More context is described in https://github.com/dotnet/dnceng/issues/5074#issuecomment-3186040770.

(Previously, we would have a dedicated queue for each API level, thus sending a workitem to specific queue would equal running on that API level.)

Requirements

- Specify which API levels to use at the XHarnessAndroidWorkItem
- Start emulators for specified API levels (the "multi" queue does NOT start emulators by default)
- Reported results should be distinguishable if the same workitem is run on multiple API levels

Current support

https://github.com/dotnet/arcade/blob/main/src/Microsoft.DotNet.Helix/Sdk/CreateXHarnessAndroidWorkItems.cs

Related xharness item

https://github.com/dotnet/xharness/issues/1459