Integration tests improvements

[denis256]

Describe the solution you'd like
Improve existing integration tests approach:

• split test files by tested functions to avoid large files and merge conflicts
• use terragrunt execution functions like runTerragruntCommandWithOutput() to print output to logs to help future debugging in case of errors
• validate expected errors with require.Error() to avoid null value failures

Describe alternatives you've considered
N/A

Additional context
N/A