Update documentation for from_raw_parts

Fixes #19269.
Lifetime guide -> ownership guide
impl Clone for Cow
small doc fixes

We don't need this &mut, and vec could use []s
Add test for #18908
fix expand_quote_ty function as parse_ty was changed and needs no arguments now
Fix typo in reference.md
Allow trailing commas in array patterns and attributes
Simplify `RefCell` code a bit, make `deref` a no-op.
std: Remove implicit shrinking from hash_map.

Implements fn shrink_to_fit for HashMap.
std: Change the behavior of `reserve` for HashMap.

HashMap's `reserve` method now takes as an argument the *extra* space
to reserve.

[breaking-change]
std: add tests for the Vec<u8> Writer impl
std: add Reader impl for &[u8]
rustdoc: Check for href when prepending rootPath

Fixes #18354.
better wording
replace 'but' with 'and'
Improve documentation of checked_* functions
Update comment to current file path for intrinsics
lldb: Fix pretty printer for nullable-opt enums with fat pointers.
gdb: Fix pretty printer for nullable-opt enums with fat pointers.