Release v0.3.1

This is an experimental pre-release intended for evaluation and feedback only.

Maven artifacts are on the GitLab package registry: https://gitlab.com/bitcoinj/secp256k1-jdk/-/packages

Minimum JDK requirements are:

secp-api: 9
secp-bouncy: 9
secp-ffm: 25

Notable changes include

• secp-bouncy: Update Bouncy Castle to 1.85 and use the Bouncy Castle BIP340Signer for Schnorr signing and verification.
• secp-ffm: Use Arena.ofConfined() for all MemorySegment allocation.

See the CHANGELOG for further details.