Follow-up: resolve languages with multiple variants

Background

When a language has multiple variants (e.g., javascript and js, python and py), they appear stacked in the "Code Suggestions acceptance by IDE" chart on the GitLab Duo and SDLC trends dashboard. The variant metrics need to be merged so that different naming conventions for the same language are consolidated into a single entry.

Related Discussion: See !215281 (comment 2934298150) for the original discussion that led to this follow-up.

Possible Solution

• Use file extension mappings from code_suggestions_languages.js
• Merge variant metrics at the data source level