4.0.0 Stable Release

This release was delayed to be able to incorporate a better cross-contract API, in the future these stable releases will come more frequently.

There has been a lot changed since the last stable version (3.1.0) so to track changes, the releases or changelog should be used.

A high-level explanation of the changes can be found in this discussion and a link to a migration document will be added here once completed.

Changes since `4.0.0-pre.9`

Updated cross-contract, ext API for new NEP264 functionality. PR 742
- More details on the API change can be found here
- This API uses a default weight of 1 with no static gas, but this weight, the static gas, and the attached deposit can all be modified on any external call
- ext methods are added to each #[near_bindgen] contract struct by default and for each method for convenience
Updated nearcore crates used for unit testing to version 0.13.0. PR 820
- Removed outcome function from MockedBlockchain (incomplete and misleading data)
- Changed created_receipts to return owned Vec instead of reference to one
- receipt_indices field was removed from Receipt type in testing utils
Deprecate and remove near-sdk-sim. Removes sim proxy struct from #[near_bindgen]. PR 817
- If near-sdk-sim tests can't be migrated to workspaces-rs, 4.0.0-pre.9 version of near-sdk-rs and near-sdk-sim should be used
Optimized read_register to read to non-zeroed buffer. PR 804
Switched Rust edition for libraries to 2021. PR 669