refactor(common): improve dayPeriods-related types in generate-locales-tool (#45714)

Update some TypeScript types in `generate-locales-tool/day-periods.ts`
to more closely reflect the actual shapes of the returned objects.

Examples of the related raw JSON data for the `en` locale can be seen
here:
- [dayPeriods][1]
- [dayPeriodRules][2]

[1]: https://github.com/unicode-org/cldr-json/blob/41.0.0/cldr-json/cldr-dates-full/main/en/ca-gregorian.json#L223-L300
[2]: https://github.com/unicode-org/cldr-json/blob/41.0.0/cldr-json/cldr-core/supplemental/dayPeriods.json#L404-L427

PR Close #45714

packages/common/locales/generate-locales-tool/day-periods.ts

@@ -12,8 +12,16 @@ import {CldrLocaleData} from './cldr-data';
  * Returns data for the chosen day periods
  */
 export function getDayPeriods(localeData: CldrLocaleData, dayPeriodsList: string[]): {
-  format: {narrow: string[], abbreviated: string[], wide: string[]},
-  'stand-alone': {narrow: string[], abbreviated: string[], wide: string[]}
+  format: {
+    narrow: Record<string, string>,
+    abbreviated: Record<string, string>,
+    wide: Record<string, string>
+  },
+  'stand-alone': {
+    narrow: Record<string, string>,
+    abbreviated: Record<string, string>,
+    wide: Record<string, string>
+  }
 } {
   const dayPeriods = localeData.main(`dates/calendars/gregorian/dayPeriods`);
   const result: any = {};
@@ -39,7 +47,8 @@ export function getDayPeriods(localeData: CldrLocaleData, dayPeriodsList: string
  * @returns string[]
  */
 export function getDayPeriodRules(
-    localeData: CldrLocaleData, language = localeData.attributes.language): {[key: string]: []} {
+    localeData: CldrLocaleData,
+    language = localeData.attributes.language): Record<string, string|[string, string]> {
   const dayPeriodRules = localeData.get(`supplemental/dayPeriodRuleSet/${language}`);
   const rules: any = {};
   if (dayPeriodRules) {