Rolling up PRs in the queue

Closes #13313 (Fix typo in README.md)
Closes #13311 (Fix inner attribute syntax from `#[foo];` to `#![foo]`)
Closes #13309 (Add stdlib docs to the Linux binary tarball.)
Closes #13308 (syntax: remove obsolete mutability from ExprVec and ExprRepeat.)
Closes #13306 (TrieSet should impl Set/MutableSet; add with_capacity to PriorityQueue/SmallIntMap)
Closes #13303 (Register new snapshots)
Closes #13274 (Added grow_fn and retain to Vec)