Optionally disable test tracing colors (#2374)

* Optionally disable test tracing colors

* Fix lint

Author: heaths

sdk/core/azure_core_test/README.md

@@ -125,6 +125,12 @@ For example, if you wanted to see debug information from all sources by default
 RUST_LOG=debug,test-proxy=trace cargo test
 ```
 
+ANSI colors are written to the terminal even if redirected to a file. To disable writing ANSI color sequences, pass `NO_COLOR=1`:
+
+```bash
+NO_COLOR=1 RUST_LOG=debug,test-proxy=trace cargo test
+```
+
 [PowerShell]: https://learn.microsoft.com/powershell/scripting/install/installing-powershell
 [Test Proxy]: https://github.com/Azure/azure-sdk-tools/blob/main/tools/test-proxy/Azure.Sdk.Tools.TestProxy/README.md
 [Test Resources]: https://github.com/Azure/azure-sdk-tools/blob/main/eng/common/TestResources/README.md

sdk/core/azure_core_test/src/recorded.rs

@@ -89,6 +89,7 @@ fn init_tracing() {
         tracing_subscriber::fmt()
             .with_env_filter(EnvFilter::from_default_env())
             .with_span_events(FmtSpan::NEW | FmtSpan::CLOSE)
+            .with_ansi(std::env::var("NO_COLOR").map_or(true, |v| v.is_empty()))
             .with_writer(std::io::stderr)
             .init();
     }