Rollup merge of #89546 - joshtriplett:grow-metadata-faster, r=petrochenkov
Rollup merge of #89546 - joshtriplett:grow-metadata-faster, r=petrochenkov

Make an initial guess for metadata size to reduce buffer resizes

When reading metadata, the compiler starts with a `Vec::new()`, which will need to grow repeatedly as the metadata gets decompressed into it. Reduce the number of resizes by starting out at the size of the compressed data.

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