[Feature] Configurable Lint and Test each iteration

[ryanpeach]

What problem or use case are you trying to solve?

Openhands needs to be able lint and test each iteration using custom lint commands, just like aider's configs:

lint-cmd, auto-lint, test-cmd, auto-test

Describe the UX of the solution you'd like

Add the following to config.toml

[sandbox]
enable_auto_lint # already exists
lint_cmd
enable_auto_test 
test_cmd # example: pytest

Do you have thoughts on the technical implementation?

docker run commands should be enough right?

Describe alternatives you've considered

Additional context