Proposal:Standardize Sinitic language tags including Mandarin based on IETF BCP 47 standard

Standardize Sinitic language tags including Mandarin based on IETF BCP 47 standard
Proposal status:	Draft (under way)
Proposed by:	快乐的老鼠宝宝
Tagging:	`name:zh=*` Data item
Applies to:
Definition:	Sinitic/Chinese/Mandarin language tags
Statistics:

Use name:zh-Hans=*, name:zh-Hant=* for names that used across different Sinitic/Chinese languages
Use name:zh-Hans-REGION=*, name:zh-Hant-REGION=* and replace the old name:zh-REGION=*, name:zh-REGION=*
- This part should already be done for most nodes, ways, and relations.
Use name:cmn-Hans=*, name:cmn-Hant=* for names that used in Mandarin languages (mostly Modern Standard Mandarin)
- The name:cmn-Hans=*, name:cmn-Hant=* would be a supplement tag instead of the main tag. Always fill zh-* tags when filling cmn-* tags.
Introduce name:cmn-Latn-variant=*, name:cmn-Latn-REGION-variant=* as supplement tags for names that used in Mandarin languages (mostly Modern Standard Mandarin) in romanizations. The old name:zh-Latn-variant=*, name:zh-Latn-REGION-variant=* tags will still be the main tag for Mandarin romanizations.
- name:zh-Latn-pinyin=* will still be the main tag while name:cmn-Latn-pinyin=* will be introduced as a supplement tag, and so on.

WIP

Old titles

Improve Chinese Language Code Conformity to BCP47 Standards
Standardize transliteration language tag of Mandarin language based on IETF BCP 47 standard
Standardize Mandarin language tags based on IETF BCP 47 standard