test-uitls: fix test output not being captured by cargo test

Rust’s `libtest` has a… limitation where it doesn’t capture data
written directly to `std::io::stdout` or `std::io::stderr` (see
rust-lang/rust#90785).  Since we are test
logger to use the latter, none of the log messages are captured by the
test harness.

The solution is to use `TestWriter` as the writer instead which
cooperates `libtest` better.

Issue: near#4490

Author: mina86

test-utils/logger/src/lib.rs

@@ -20,7 +20,7 @@ fn setup_subscriber_from_filter(mut env_filter: EnvFilter) {
     let _ = tracing_subscriber::fmt::Subscriber::builder()
         .with_span_events(tracing_subscriber::fmt::format::FmtSpan::CLOSE)
         .with_env_filter(env_filter)
-        .with_writer(std::io::stderr)
+        .with_writer(tracing_subscriber::fmt::TestWriter::new())
         .try_init();
 }