Make the logger replaceable #1568

What happens

All logging goes through the debug package, under six namespaces (testcontainers, testcontainers:containers, :compose, :build, :pull, :exec). The only control is the DEBUG environment variable.

• Logs cannot be sent to the application's logger or to a test reporter.
• The level cannot be set from code.
• Nothing is shown by default, so the first pull of a large image looks like a hang.
• When NODE_ENV is test, the logger switches its output from stderr to console.log.

Expected

• A logger interface that can be replaced: setLogger({ debug, info, warn, error }).
• The debug-based logger stays the default, so DEBUG=testcontainers* keeps working.
• Container, build, pull and exec output remain separable.

Where

packages/testcontainers/src/common/logger.ts and its exported instances.

Notes

• Go has log.SetDefault(logger). Java logs through SLF4J, so the application chooses the backend.
• log is exported from the package today, so its shape is public API.

Dependencies

• Nothing blocks this. It can start now.