Adds opt-in log capture via withLogCapture() and getCapturedLogs().

[VolkovIO]

Summary

GenericContainer.getLogs() can return empty output when container startup fails or the container exits very quickly (e.g. one-shot commands). This PR adds an opt-in mechanism to capture container logs in memory so they can still be retrieved after a failed start.

Changes

• Add withLogCapture() to enable in-memory log capture (disabled by default).
• Add getCapturedLogs() to retrieve captured stdout/stderr.
• Add tests covering default behavior (no capture) and enabled capture on startup failure.

Rationale

The implementation reuses the existing log consumer mechanism by registering a ToStringConsumer when log capture is enabled, without changing default behavior or getLogs() semantics.

Testing

• GenericContainerLogCaptureTest verifies:
  • no captured logs by default when startup fails
  • captured logs contain container output when withLogCapture() is enabled

Fixes #11215