Prepare for Polkadot launch and Substrate 2.0 freeze

[gavofyork]

On the Substrate side:

• Lazy reaping: Lazy reaping #4895
• Lazy payouts: Lazy payouts #4474
• Offchain Phragmen: Offchain Phragmén BREAKING. #4517
• Migrate storage maps: Migrate storage maps to use twox64_concat or blake2_128_concat #4917
• Dispatch & block weights CC @shawntabrizi et al.
  • Macro: Benchmark macro #4962
  • Pallets: Benchmarking for Pallets #4876
  • on_initialize/on_finalize
  • Root calculation with extrinsic benchmarks. Add storage root recalculation time to benchmarks #5035
  • Root calculation (amortized).
  • Rest of block execution init/teardown in executive.
  • Combine benchmark timing and complexity analysis to derive weight predictors (Regression algorithm for runtime benchmarks #5288).
  • Create sufficiently accurate weight formula, based solely on call data (not on state!), refactoring dispatches as necessary.
  • Implement weights through all pallets (FunctionOf) (tracking issue: Document and Calculate Weights for Pallets #5596).
• Assign unique storage names to pallets: Assign unique storage names to pallets. #5010
• Stability
  • Memory leaks (Responsible Memory Usage polkadot-sdk#562, Make sure we poll authority event stream until all events are processed  #5608)
  • Network connections leaks (Network connection leak #4679, libp2p-next #5278)
  • Threading issues & deadlocks (Move spawning tasks from thread pools to Service's TaskManager for block importing #5647, Remove TaskManagerBuilder #5725 )
• Refactor democracy away from batch processing (Refactor Democracy #5248)
• Fix prime member selection (Prime member selection in Phragmen Elections #5290)

On the Polkadot side:

• Corresponding PR for Lazy reaping #4895 and Composite accounts #4820: Updates needed for substrate #4820 (composite accounts) polkadot#834
• Upgrade/migrate Kusama with that ^^^
• Corresponding PR for Migrate storage maps to use twox64_concat or blake2_128_concat #4917.
• Upgrade/migrate Kusama with the corresponding PR for Migrate storage maps to use twox64_concat or blake2_128_concat #4917

[kianenigma]

IMO this is also worth fixing #2494

[gavofyork]

That's very much on-trivial and there may be no good solution. Until we have a solution that works with staking being off-chain, then I would leave it.

[JoshOrndorff]

Create sufficiently accurate weight formula, based solely on call data (not on state!), refactoring dispatches as necessary.

A few months ago I came up with this pattern where the weight of a call seems like it shold depend on state. The caller passes the expected value of the state, the weight is calculated based on that expected value, and the call ensures that the passed value is accurate.

https://github.com/substrate-developer-hub/recipes/blob/fc4c625addf43cb5088a73f6f0559db24fc2bd95/pallets/weights/src/lib.rs#L144-L149