Add support for worker.config.json being determined by build target

Currently, we manually choose which PS worker contains the top-level worker.config.json file (`powershell/worker.config.json`) by adding it as a contentFile to the build output. Add a system that uses targets allowing the consumer of the worker to set PowerShellWorkerConfigVersion and choose which worker config takes precedence:

Rough sketch:
Target file
```xml

<_PowershellWorkerConfigCopyDependsOn>
$(_PowershellWorkerConfigCopyDependsOn);
_PowershellWorkerConfigVersionCheck_{Version}

<_PowershellWorkerVersion Condition="'$(_PowershellWorkerVersion)' < '{Version}'>{Version}
<_PowershellWorkerConfig Condition="'$(_PowershellWorkerVersion)' == '{Version}'>this_instances_worker_config

```

For csproj
```xml
7.6
```