Bump Java to 25 for teku and besu builds

[barnabasbusa]

Summary

• Teku master upgraded targetJavaVersion to Java 25 (consensys/teku#10567), causing the scheduled teku build to fail with the JDK 21 currently installed by install-deps.
• Bumps both teku and besu to JDK 25. Besu still pins sourceCompatibility = 21 but builds fine on a newer JDK.

Fixes the failure in run 25982909839.

Test plan

• Trigger a teku master build on this branch and confirm it succeeds. — run 26029821633 ✅ (amd64 + arm64 + manifest, tag jdk25-test-147ba3)
• Trigger a besu main build on this branch and confirm it succeeds. — run 26029819949 ✅ (amd64 + arm64 + manifest, tag jdk25-test-147ba3)

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Generated by Claude Code

[qu0b-reviewer]

🤖 qu0b-reviewer

Looks good — clean bump + a well-scoped syntax refactor. No blockers. 🦋

Java 25: No known advisories for Temurin/OpenJDK 25. Forward compatibility claim (target stays at 21 for Besu) is correct — JDK 25 can build code targeting 21 just fine.

: override syntax: Consistent — two split(':', 1) calls (main branches + alt_repos), both using maxsplit=1. The alt_repos path also correctly prepends the repo prefix to the override tag, matching the existing pattern for non-overridden branches.

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_{Reviewed @ b190a7b7}