Chinese locales: Set first_weekday to 2 (bug 24682).

The first day of the week in China (Mainland) should be Monday according
to the national standard GB/T 7408-2005.  References:

* https://www.doc88.com/p-1166696540287.html
* https://unicode-org.atlassian.net/browse/CLDR-11510

	[BZ #24682]
	* NEWS: Mention this bug fixed.
	* localedata/locales/bo_CN (first_weekday): Add, set to 2 (Monday).
	* localedata/locales/ug_CN (first_weekday): Likewise.
	* localedata/locales/zh_CN (first_weekday): Likewise.

(cherry picked from commit c0fd3244)