ConanfileProbe no longer shows output in verbose mode due to Conan 2.x CLI changes

Since upgrading to Conan 2.x, the ConanfileProbe in Qbs no longer shows any output in verbose mode. This regression is due to Conan 2's revised CLI output policy. Unlike Conan 1.x, which printed both human-readable and machine-readable output to stdout, Conan 2.x separates them:

• Machine-readable output (e.g., JSON with --format=json) → stdout

• Human-readable logs, warnings, and status messages → stderr

Currently, ConanfileProbe only reads from stdout, and thus misses the relevant information output by Conan 2.x.

This behavior is mentioned in the Conan issue:
🔗 https://github.com/conan-io/conan/issues/12200

Expected Behavior:

In verbose mode, ConanfileProbe should capture and display output from stderr to reflect Conan's logs.

Actual Behavior:

With Conan 2.x, no verbose output is shown in Qbs because ConanfileProbe only captures stdout.
This behavior can be easily observed with command:

conan install . 1>out.log 2>err.log