Adopt to Arm Template strategy for Azure Eventgrid

[rakshith91]

Currently, there are a lot of env variables in eventgrid tests.yml

Use the arm template instead to reduce maintainance.

To add a deployment of arm templates you'll need a test-resources.json file and parameter DeployArmTemplate: true to your tests.yml file. The former you can probably take from the .NET/JS/Java sdks.

[lmazuel]

Not GA required, I moved that to March milestone