Add space between columns in runner table

🧩 Problem

Based on !74071 (merged), we were able to prevent some complete overlap of data within the runner table, but it still looks like things are overlapping since there is no space between the columns (can apply to the cell data and column headers). In https://gitlab.com/gitlab-org/gitlab/blob/02ab624c7642d0e1eaeb580e87fcdd4564913b28/app/assets/javascripts/runner/components/runner_list.vue#L20 we define a special CSS class with a margin that should be updated to reflect the standard 16px spacing between columns from the Pajamas table component

💡 Proposal

Add padding for column header cells and data cells. It looks like we are using gl-p-5 for that in the pipelines table today.