feat: bump stellar its to v2.1.0

[rista404]

why

upgrade ITS to axelarnetwork/axelar-amplifier-stellar#383

Part of CPI-293

how

---

Note

High Risk
On-chain ITS upgrade and breaking set_flow_limit ABI affect interchain token flow limits; incorrect config or failed upgrades impact production Stellar ITS.

Overview
Bumps Stellar Interchain Token Service to v2.1.0 on mainnet and the quarterly Stellar testnet entry, and records the rollout in chain config plus a new release note.

Chain config updates wasmHash and version for InterchainTokenService (1.4.1 → 2.1.0) on Stellar mainnet and testnet. On testnet it also refreshes AxelarGateway (2.0.1), AxelarOperators (1.1.4), and AxelarGasService (2.0.1) wasm hashes/versions for the same Stellar chain block.

Release doc (releases/stellar/2026-06-ITS-2.1.0.md) documents v2.1.0: per-token flow limiter delegation (operator-managed roles; limiters can call set_flow_limit), alignment with EVM TokenManager, and a breaking on-chain ABI—set_flow_limit now takes a leading caller: Address with auth. It includes upgrade steps and post-deploy checklists.

stellar/utils.ts lengthens Soroban tx timebound to 600s and derives MAX_RETRIES from that window so polling does not report failure while a tx can still land after the previous ~30s cap.

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CPI-293

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