ink! 4.0-beta tracking

[ascjones]

We agreed at the team retreat what needs to be done for ink! 4.0 beta: essentially any contract ABI breaking changes MUST be included in this release. Breaking changes to the language itself (e.g. shared events) can be added in future beta pre-releases.

This first pre-release will be beta, followed by beta.1, beta.2 etc.

Must haves

• Add support for language level errors (LangError) #1450 @HCastano
• Stabilize four storage functions #1462 @agryaznov
  • Blocked on updating substrate-contract-node to latest polkadot release, a follow up to Update to polkadot-v0.9.31 paritytech/substrate-contracts-node#156 @athei
• revert Conditional Codegen for Messages, Constructors and Events #1458 @SkymanOne
• Replace Mapping::insert_return_size with Mapping::insert #1463 @lean-apple
• Fix and refactor fallible constructors #1483 @ascjones

Nice to haves

• Generate metadata for constructor return type #1460 @SkymanOne
• cargo-contract extrinsics compatibility Update to weights v2 cargo-contract#809 @ascjones

Other todos

• Prepare a release PR