[FIX] spreadsheet: faster compute format

`getReportMeasures` is called repeatedly for every pivot function.
In HBA's demo spreadsheet it takes up to 30% of the loading time.

Part-of: odoo/odoo#138166

addons/spreadsheet/static/src/pivot/pivot_data_source.js

@@ -51,11 +51,6 @@ export default class PivotDataSource extends OdooViewsDataSource {
         return model;
     }
 
-    getReportMeasures() {
-        this._assertDataIsLoaded();
-        return this._model.getReportMeasures();
-    }
-
     /**
      * @param {string[]} domain
      */

addons/spreadsheet/static/src/pivot/pivot_functions.js

@@ -68,7 +68,7 @@ const ODOO_PIVOT = {
     computeFormat: function (pivotId, measureName, ...domain) {
         pivotId = toString(pivotId.value);
         const measure = toString(measureName.value);
-        const field = this.getters.getPivotDataSource(pivotId).getReportMeasures()[measure];
+        const field = this.getters.getPivotDataSource(pivotId).getField(measure);
         if (!field) {
             return undefined;
         }

addons/spreadsheet/static/src/pivot/pivot_model.js

@@ -4,7 +4,6 @@ import { _t } from "@web/core/l10n/translation";
 import { Domain } from "@web/core/domain";
 import { sprintf } from "@web/core/utils/strings";
 import { PivotModel } from "@web/views/pivot/pivot_model";
-import { computeReportMeasures } from "@web/views/utils";
 
 import * as spreadsheet from "@odoo/o-spreadsheet";
 import { PERIODS } from "@spreadsheet/pivot/pivot_helpers";
@@ -201,10 +200,6 @@ export class SpreadsheetPivotModel extends PivotModel {
         return field.string + (aggregateOperator ? ` (${PERIODS[aggregateOperator]})` : "");
     }
 
-    getReportMeasures() {
-        return computeReportMeasures(this.metaData.fields, this.metaData.fieldAttrs, []);
-    }
-
     //--------------------------------------------------------------------------
     // Cell missing
     //--------------------------------------------------------------------------