Rollup merge of #69973 - tspiteri:const-int-conversion-since, r=dtolnay
Rollup merge of #69973 - tspiteri:const-int-conversion-since, r=dtolnay

Update stable-since version for const_int_conversion

Since #69373 was not merged in time for 1.43.0 beta, update to `since = "1.44.0"`.

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