Release 2.0.0

[cuviper]

• MSRV: Rust 1.64.0 or later is now required.

• The "std" feature is no longer auto-detected. It is included in the
  default feature set, or else can be enabled like any other Cargo feature.

• The "serde-1" feature has been removed, leaving just the optional
  "serde" dependency to be enabled like a feature itself.

• IndexMap::get_index_mut now returns Option<(&K, &mut V)>, changing
  the key part from &mut K to &K. There is also a new alternative
  MutableKeys::get_index_mut2 to access the former behavior.

• The new map::Slice<K, V> and set::Slice<T> offer a linear view of maps
  and sets, behaving a lot like normal [(K, V)] and [T] slices. Notably,
  comparison traits like Eq only consider items in order, rather than hash
  lookups, and slices even implement Hash.

• IndexMap and IndexSet now have sort_by_cached_key and
  par_sort_by_cached_key methods which perform stable sorts in place
  using a key extraction function.

• IndexMap and IndexSet now have reserve_exact, try_reserve, and
  try_reserve_exact methods that correspond to the same methods on Vec.
  However, exactness only applies to the direct capacity for items, while the
  raw hash table still follows its own rules for capacity and load factor.

• The Equivalent trait is now re-exported from the equivalent crate,
  intended as a common base to allow types to work with multiple map types.

• The hashbrown dependency has been updated to version 0.14.

• The serde_seq module has been moved from the crate root to below the
  map module.

[ds-cbo]

With hashbrown 0.14 relaxing its MSRV to 1.63.0 to support Debian stable, would it also be possible to relax indexmap's MSRV to 1.63.0 along with it? That would make indexmap v2 usable for hyperium/h2 with the same 1.63.0 MSRV, and prune the duplicated indexmap dependency (currently both v1.9.6 for h2 through hyper and v2.0.0 for toml_edit) from our compile trees.

Also see discussion here: hyperium/h2#698

Update: My bad, I just saw the comment here that hashbrown hasn't released an updated 0.14 yet with the relaxed MSRV, and that it's still a hot topic. I'm sorry for being impatient.

[cuviper]

How about this: I can make the update here with --ignore-rust-version in CI to get past hashbrown's published MSRV, so it will be in place if/when hashbrown does publish that change.

[cuviper]

Published via #276.