Naive implementation of allowing env override (Azure#37780)

* naive implementation of allowing env override

Co-authored-by: Christopher Scott <[email protected]>

Author: scbedd

sdk/core/Azure.Core.TestFramework/README.md

@@ -366,6 +366,8 @@ public KeyClientLiveTests(bool isAsync, KeyClientOptions.ServiceVersion serviceV
 }
 ```
 
+__Note:__ A user can set the environment variable PROXY_DEBUG_MODE to a truthy value prior to invoking, just like if they set `UseLocalDebugProxy` in their code.
+
 In order to debug the test proxy, you will need to clone the [azure-sdk-tools](https://github.com/Azure/azure-sdk-tools) repo. The best practice is to first create a fork of the repo, and then clone your fork locally.
 
 Once you have cloned the repo, open the [Test Proxy solution](https://github.com/Azure/azure-sdk-tools/blob/main/tools/test-proxy/Azure.Sdk.Tools.TestProxy.sln) in your IDE.

sdk/core/Azure.Core.TestFramework/src/TestProxy.cs

@@ -60,6 +60,10 @@ static TestProxy()
 
         private TestProxy(string proxyPath, bool debugMode = false)
         {
+            bool.TryParse(Environment.GetEnvironmentVariable("PROXY_DEBUG_MODE"), out bool environmentDebugMode);
+
+            debugMode |= environmentDebugMode;
+
             ProcessStartInfo testProxyProcessInfo = new ProcessStartInfo(
                 s_dotNetExe,
                 $"\"{proxyPath}\" --storage-location=\"{TestEnvironment.RepositoryRoot}\"")