[charts] Reduce ChartsWrapper bundle size

[sai6855]

PR #19257 fixed toolbar positioning by switching ChartsWrapper from flex to CSS grid. The fix itself is correct and remains unchanged, but it introduced 5 small helpers that each duplicated branching logic along with repeated gridTemplate* property names.

This PR simplifies the implementation by:

• Collapsing the 5 helper functions into a single inline branch inside the styled callback.
• Ensuring each grid-template* property name is declared only once.
• Replacing the :has() block’s runtime split/map/join chain with a single boolean check.

The result keeps the same layout behavior while reducing duplicated runtime and bundle output.

[code-infra-dashboard]

Deploy preview

https://deploy-preview-22463--material-ui-x.netlify.app/

Bundle size

Bundle	Parsed size	Gzip size
@mui/x-data-grid	0B(0.00%)	0B(0.00%)
@mui/x-data-grid-pro	0B(0.00%)	0B(0.00%)
@mui/x-data-grid-premium	0B(0.00%)	0B(0.00%)
@mui/x-charts	▼-337B(-0.09%)	▼-58B(-0.05%)
@mui/x-charts-pro	▼-337B(-0.07%)	▼-59B(-0.04%)
@mui/x-charts-premium	▼-337B(-0.06%)	▼-55B(-0.03%)
@mui/x-date-pickers	0B(0.00%)	0B(0.00%)
@mui/x-date-pickers-pro	0B(0.00%)	0B(0.00%)
@mui/x-tree-view	0B(0.00%)	0B(0.00%)
@mui/x-tree-view-pro	0B(0.00%)	0B(0.00%)
@mui/x-license	0B(0.00%)	0B(0.00%)

Details of bundle changes

Performance

Total duration: 918.03 ms -34.72 ms^(-3.6%) | Renders: 30 ⁽⁺⁰⁾ | Paint: 1,284.69 ms -34.44 ms^(-2.6%)

Test	Duration	Renders
LineChart with big data amount (with marks)	89.88 ms 🔺+18.73 ms(+26.3%)	2 (+0)
ScatterChartPro with big data amount and zoomed in (single renderer)	11.36 ms 🔺+3.04 ms(+36.6%)	2 (+0)
ScatterChartPro with big data amount and zoomed in (batch renderer)	9.69 ms 🔺+1.74 ms(+21.9%)	2 (+0)

11 tests within noise — details

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[Copilot]

Pull request overview

This PR refactors the styled callback in ChartsWrapper to inline what were five separate helpers (getJustifyItems, getAlignItems, getGridTemplateAreas, getTemplateColumns, getTemplateRows) into a single branching block. It also replaces the previous split/map/join runtime computation for the toolbar's grid areas with a boolean (twoColumns) tracked at the same time as the columns string. The goal is reducing duplicated branch logic and bundle size while preserving the layout behavior introduced by #19257.

Changes:

• Replace five branching helpers with a single inline if/else if/.../else chain computing areas, rows, columns, and twoColumns.
• Use small lookup objects (JUSTIFY_ITEMS, ALIGN_ITEMS) for justifyItems/alignItems resolution.
• Compute the toolbar grid-template-areas string from twoColumns instead of splitting gridTemplateColumns.

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