starknet_api: escape the Pedersen image in Blake2 contract address derivation

[ron-starkware]

Stack — part 2 of 9 (base: #14811). Targets 0.14.5.

Makes the Blake2 arm of calculate_contract_address escape the Pedersen image: the raw BLAKE2s address is incremented (wrapping mod L2_ADDRESS_UPPER_BOUND, skipping the reserved 0x0/0x1) until no Pedersen derivation can reach it.

A Pedersen output is always the x-coordinate of a STARK curve point, so the escaped address is provably unreachable by any Pedersen derivation — a funded-but-undeployed Blake2 address cannot be front-run through DeployAccount v1/v3 or the deploy syscall, even by an attacker with a discrete-log oracle. The two address spaces are therefore disjoint, and the scheme is readable off any address with one residuosity check.

• pedersen_reachable(a) = is_curve_x(a) or (a < SECOND_LIFT_BOUND and is_curve_x(a + ADDR_BOUND)), with SECOND_LIFT_BOUND = p - ADDR_BOUND = 17·2^192 + 257.
• BLAKE2s runs exactly once; each escape step is a square-root check, never a re-hash. Mean 1.02 increments over 20k random starts (max 17); the loop is deliberately uncapped.

Tests pin the five frozen derivation vectors (0/1/2/3/7 escape steps) and the pedersen_reachable truth table — the same vectors the Cairo OS, the cairo compiler (starkware-libs/cairo#10214) and cairo-native pin.

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• starknet_os_flow_tests: prove a block with a DeployAccount v4 end-to-end #14819
• apollo_starknet_os_program,starknet_os: add the deploy_v2 syscall to the OS #14818
• blockifier: add the deploy_v2 syscall (Blake2 contract address derivation) #14817
• apollo_http_server,apollo_gateway_types: accept DeployAccount v4 at the gateway #14816
• blockifier: enable DeployAccount v4 execution #14815
• starknet_os: support DeployAccount v4 Blake2 address derivation in the OS #14814
• starknet_api: add DeployAccount v4 transaction type (Blake2 address derivation) #14813
• starknet_api: escape the Pedersen image in Blake2 contract address derivation #14812 👈 (View in Graphite)
• starknet_api: make contract address derivation hash-pluggable #14811
• main

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