SIMD-0391: Upgrade BPF Stake Program to v5.1.0 (fixed-point warmup/cooldown)

Active on mainnet-beta (epoch 1026), testnet (epoch 1011) and devnet (epoch 1131).

Minimum versions: Agave v4.2.0-beta.0, Firedancer v26.08.0, Frankendancer v0.1102.40201.

Introduced in anza-xyz/agave PR #9637.