[TheMerge] Kiln tracking

[yperbasis]

(Supersedes Issue #3078)

See Kiln 🔥🧱 Milestones.

• M0: Implementation started
  New Engine API semantics (Kiln v1) #3340
  Add Beacon payloads to body downloader prefetch #3482
  Fix stall on unwind in handleForkChoice #3536
  Fix Reorg Indexing on Proof-of-Stake #3538
  added sleep for NewPayloadV1 and Forkchoice #3561
  Fix coinbase in stage_mining_exec #3564
  Fixed get-payload and Hanging ForkChoice #3575
  Refactor payload building #3592
  Expose eth API on the same ports as engine API #3633
  Handle a corner case in forkchoiceUpdated #3640
  Fixed forkid for mergeBlock #3686
  fixed transition warning in Prysm #3687
• M1: Kiln v1 Spec Implemented
  • pass all released consensus test vectors
  • Run against mergemock
  • Geth based Engine API test cases
• M2: Kiln v2 Spec Implemented
  adding engine_ExchangeTransitionConfigurationV1 #3454
  Added Engine Authentication [JWT] #3531
  PrevRandao Renaming #3616
  fixed JWT authentication port #3689
• M3: Many-to-Many Interop – 2 or more EL and CL teams perform interop testing
• M4: Weekly devnet – Weekly devnet build for more in depth testing
• M5: All-to-All persistent testnet – All ready EL and CL teams create a long-lived devnet
• M6: Kiln 🔥🧱 code released – clients release Kiln 🔥🧱 code for public consumption