Rollup merge of #74142 - pickfire:patch-1, r=dtolnay
Rollup merge of #74142 - pickfire:patch-1, r=dtolnay

Liballoc use vec instead of vector

Keep congruency with other parts, full word vector is rarely used.

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