Add bar list chart visualization component

What does this MR do and why?

Adds a BarListChart visualization component, Storybook stories, and specs for the analytics dashboards system.

Renders a horizontal bar list: one row per entry, with a right-aligned category label, a full-width track, a proportional filled bar, and an 89% · 85.6k label past the bar's end. No x-axis or gridlines.

Storybook only for now. Deliberately not registered in visualizations/index.js, so it isn't yet a selectable dashboard visualization type — that comes with the follow-up panel work.

Design notes:

• Bar length is each row's share of the total, not scaled against the largest row, so a bar's length reads as its percentage of the whole. The component doesn't sort or derive share — the caller does, so an "Other (N)" rollup row can carry the true total's share.
• Built on base GlChart, not GlBarChart. GlBarChart builds its own series and appends any caller option.series as an extra series rather than merging, so a series label and showBackground are unreachable, and fill opacity is fixed at 20%. This design needs all three.
• Fills its container height, same as area_chart.vue / line_chart.vue.

References

• https://gitlab.com/gitlab-org/gitlab/-/work_items/623319+
• https://gitlab.com/gitlab-org/gitlab/-/work_items/624280+
• https://gitlab.com/gitlab-org/gitlab/-/work_items/622518+

Screenshots or screen recordings

full size	smaller size

How to set up and validate locally

1. yarn storybook:start
2. Open http://localhost:6006/?path=/story/analytics-analytics-dashboards-components-visualizations-bar-list-chart--default
3. Step through the five stories: Default, LongTail, EvenDistribution, LongCategoryLabels, InDashboardPanel
4. VUE_VERSION=3 yarn jest spec/frontend/analytics/analytics_dashboards/components/visualizations/bar_list_chart_spec.js

MR acceptance checklist

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