encoding/json: clarify unmarshaling behaviour on bad fields
encoding/json: clarify unmarshaling behaviour on bad fields

Fixes #19526

Change-Id: Ifaaf454e0e89fdf4309118c2e2e6ac0d0a43c39d
Reviewed-on: https://go-review.googlesource.com/44711
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

akutz/go,golang/go,ImJasonH/go,polyverse-security/go,Cofyc/go,vsekhar/elastic-go,ImJasonH/go,codestation/go,christopher-henderson/Go,codestation/go,CAFxX/go,vsekhar/elastic-go,CAFxX/go,ImJasonH/go,vsekhar/elastic-go,josharian/go,CAFxX/go,codestation/go,akutz/go,ImJasonH/go,josharian/go,josharian/go,polyverse-security/go,codestation/go,CAFxX/go,nawawi/go,ImJasonH/go,akutz/go,Cofyc/go,vsekhar/elastic-go,golang/go,cloudflare/go,nawawi/go,polyverse-security/go,josharian/go,polyverse-security/go,josharian/go,vsekhar/elastic-go,ImJasonH/go,nawawi/go,ImJasonH/go,golang/go,Cofyc/go,golang/go,akutz/go,akutz/go,golang/go,CAFxX/go,nawawi/go,cloudflare/go,akutz/go,cloudflare/go,codestation/go,nawawi/go,cloudflare/go,akutz/go,Cofyc/go,cloudflare/go,codestation/go,cloudflare/go,CAFxX/go,polyverse-security/go,polyverse-security/go,nawawi/go,nawawi/go,cloudflare/go,CAFxX/go,Cofyc/go,Cofyc/go,codestation/go,ImJasonH/go,CAFxX/go,josharian/go,vsekhar/elastic-go,vsekhar/elastic-go,Cofyc/go,polyverse-security/go,polyverse-security/go,cloudflare/go,golang/go,akutz/go,golang/go,codestation/go,vsekhar/elastic-go,golang/go,josharian/go,Cofyc/go,nawawi/go,josharian/go