Improve the Metric Registry Populate script

[IvanIvanoff]

Changes

• The old version of the populate script was causing constraint errors
• Also break down the big populate function into multiple small ones

Ticket

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have tried to find clearer solution before commenting hard-to-understand parts of code
• I have added tests that prove my fix is effective or that my feature works