Rollup merge of #60360 - rasendubi:const-labeled-break, r=Centril
Rollup merge of #60360 - rasendubi:const-labeled-break, r=Centril

Add test case for labeled break in const assignment

Fixes #51350.

graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust