Add Terraform report to the merge request reports tab

What does this MR do and why?

Adds TerraformProvider, TerraformNavItem, TerraformPage, and TerraformContent, following the code quality report pattern, plus a View report button on the terraform widget. Row building, grouping, and summary logic move into a shared utils.js used by both the widget and the report. ReportSection also gains support for the summary subtitle and the text styling tags in supporting text, which the terraform rows need.

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