Respect the limit search param in the task overview duration chart

[warreee]

The duration chart on the task overview always requested the last 14 task instances, ignoring the number of dag runs the user picked. The dag details layout already writes that choice to the limit search param, and the dag overview page reads a value of its own, so the task page was the only view that could not be widened.

Read the same limit search param the details layout writes, falling back to the same default of 10, so the chart follows the selector and can be shared through the URL.

The remaining limit on the failed task instance query is left alone: that query only reads total_entries and never renders the rows it fetches.

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[boring-cyborg]

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