Microsoft.Web/sites/slots autoSwapSlotName should be invalid for a Linux app service plan

**Bicep version**
Bicep CLI version 0.6.18 (46dd19e8eb)

**Describe the bug**
Auto Swap is not supported for Web Apps on Linux: https://docs.microsoft.com/en-us/azure/app-service/deploy-staging-slots#Auto-Swap
I am able to configure a AutoSwapSlotName and deploy to Azure successfully, however when I attempt to deploy to the staging slot, the deployment will fail.

**To Reproduce**
```bicep
resource appService_Slot 'Microsoft.Web/sites/slots@2021-03-01' = {
name: 'staging'
location: location
parent: appService
properties:{
siteConfig: {
autoSwapSlotName:'production'
```

Start by tracing validation for Microsoft.Web/sites/slots and siteConfig.autoSwapSlotName, then check how the app service plan's Linux status is represented. Reproduce the issue with the Bicep example and add or update a regression test so the configuration is rejected for Linux plans while remaining valid where supported.

Written by the indexing model from the issue text.