Relates to #472

This updates the existing Oracle GraalVM manifests to use current Oracle-owned sources for version detection.

Changes:

• graalvm-oracle-jdk now tracks Oracle GraalVM 25.0.3 from the Oracle GraalVM 25 release notes.
• graalvm-oracle-21jdk now tracks Oracle GraalVM for JDK 21.0.11 from the Oracle GraalVM JDK 21 release notes.
• graalvm-oracle-17jdk remains at 17.0.12 and now checks the JDK 17 archive page for 17.0.12 and earlier.

Design decisions:

• The active 25 and 21 manifests keep version-specific archive URLs, with hashes from Oracle's matching .sha256 files.
• JDK 17 is not bumped to 17.0.13 or newer here because Oracle moved those CPU releases to the GraalVM OTN license/download path. The public archive page used by the current manifest only covers 17.0.12 and earlier.
• No third-party version source is used.

Validation:

• checkver.ps1 graalvm-oracle-jdk -> 25.0.3

• checkver.ps1 graalvm-oracle-21jdk -> 21.0.11

• checkver.ps1 graalvm-oracle-17jdk -> 17.0.12

• checkurls.ps1 passes for all three manifests: [1][1][0]

• I have read the Contributing Guide.

Summary by CodeRabbit

• Updates
  • GraalVM Oracle JDK 21 updated to version 21.0.11, incorporating latest improvements and updates
  • GraalVM Oracle JDK 25 updated to version 25.0.3 with the latest enhancements
  • Enhanced version detection and release verification mechanisms across all supported JDK versions for better accuracy