[Ryang-21]

What

Cuts the v17.3.0 section in CHANGELOG.md and bumps package.json to 17.3.0. It also fixes the changelog in three places:

• Adds an entry for the XDR regeneration with CAP-84, CAP-87 and CAP-88 enabled (build(xdr): regenerate schema with CAP-84 muxed contracts enabled #1795, build(xdr): regenerate schema with CAP-87 ml-dsa cost types enabled #1796, build(xdr): regenerate schema from stellar-xdr with CAP-88 ungated #1797).
• Links Update RPC and Horizon types for Protocol 30 server releases #1836 on the contract_credited and inSuccessfulContractCall entries, which linked only the upstream Horizon and RPC PRs.
• Links fix: close muxed-address gaps from #1811 #1835 on the two feat: support CAP-84 muxed contract (W...) addresses #1811 entries that it rewrote.

Why

Since v17.2.1 there is new API (CAP-84 muxed contract addresses, new XDR types, Horizon effect fields), so this is a minor bump.

A diff of the public type declarations against v17.2.1 shows no removed or renamed exports and no narrowed parameter types. These edge cases remain, and each has a changelog entry:

• inSuccessfulContractCall is now optional, so code that assigns it to a boolean fails to compile under strict. Newer RPC servers already omit it.
• AddressType, xdr.ScAddress, ContractCostType and StellarValueType gain new values, so exhaustive switches over them stop compiling.
• Several inputs that built transactions or requests the network rejects now throw early.
• new Asset("xlm", issuer) now encodes xlm rather than XLM, and Federation.Server follows redirects only when allowedRedirects is set.