Add main/init placement and read configuration file from outside

[metal3d]

Some enhancements:

• Allow to place main and init functions
• Read configuration file from the root of the project (if the command is launched outside the project)

[github-actions[bot]]

:arrow_down: Go test coverage decreased from 87.7% to 85.7% compared to 42304a6f990da4109f16171945d60d442eceaf30 Updated Package Coverages: ```diff # Package Name | Prior | New + github.com/metal3d/goreorder/cmd/goreorder | 0.0% | 71.9% + github.com/metal3d/goreorder/log | 0.0% | 83.3% + github.com/metal3d/goreorder/ordering | 87.7% | 91.8% ```

View coverage for all packages

```diff # Package Name | Coverage + github.com/metal3d/goreorder/cmd/goreorder | 71.9% + github.com/metal3d/goreorder/log | 83.3% + github.com/metal3d/goreorder/ordering | 91.8% ```