replace gl-chart wrapper components with gitlab-ui chart component

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In the interest of maintaining velocity, we have shipped charts a few places utilizing the default gl-chart echarts wrapper or by modifying the existing gl-area-chart implementation. We should replaces these instances with properly correlated gitlab-ui chart components

Line Chart implementations:

• https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8631
• https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24663