fix(charts): Stabilize ChartComponent reference in EventsChart

[sentry]

This PR addresses a static-component-definitions violation flagged by the React Compiler in static/app/components/charts/eventsChart.tsx.

Problem:
The ChartComponent used in the Chart component was being derived via an inline function getChartComponent() called directly within the render body. This meant that ChartComponent received a new identity on every render, causing React to unmount and remount the component subtree unnecessarily, and preventing compiler optimizations.

Solution:
The getChartComponent() helper function has been removed. The logic to determine the correct chart component (e.g., BarChart, LineChart, AreaChart) is now encapsulated within a useMemo hook. This ensures that ChartComponent maintains a stable reference across renders, only re-evaluating when its dependencies (chartComponent, showDaily, timeseriesData.length, forceChartType, yAxis) change. This resolves the static-component-definitions issue and allows for proper React Compiler optimization.

Legal Boilerplate

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Fixes CODING-CONVENTIONS-35D

_{Comment @sentry <feedback> on this PR to have Autofix iterate on the changes.}