Refactor: go binary instead of bash script

**why/what**
We need to port this into a go binary as part of an effort to making this available for all architectures. The script uses `awk` extensively which on `mac` is needed to install `gawk` to be able to run the script.

**definition of done**:

https://github.com/grafana/database-migrator/issues/9#tasklist-block-937eaf78-c47e-41ad-8577-51cbd154a9ad

Start by locating the existing shell script and reviewing how it uses awk, especially the parts affected by macOS needing gawk. Port that behavior into a Go binary that works across architectures and no longer requires the shell or gawk dependency; the issue does not name tests or specific files to run.

Written by the indexing model from the issue text.