Add native access JVM flag for Bouncy Castle FIPS on newer Java releases

[vharseko]

Summary

This change suppresses the Java restricted method warning emitted by Bouncy Castle FIPS when running OpenDJ on newer Java versions:

WARNING: A restricted method in java.lang.System has been called
WARNING: java.lang.System::load has been called by org.bouncycastle.crypto.fips.NativeLoader$1 in an unnamed module
WARNING: Use --enable-native-access=ALL-UNNAMED to avoid a warning for callers in this module
WARNING: Restricted methods will be blocked in a future release unless native access is enabled

The startup scripts now add --enable-native-access=ALL-UNNAMED automatically when the configured JVM supports it.

Changes

• Updated Unix startup environment handling in opendj-server-legacy/resource/bin/_script-util.sh.
• Updated Windows startup environment handling in opendj-server-legacy/resource/bin/_script-util.bat.
• Added a JVM capability check before appending --enable-native-access=ALL-UNNAMED.
• Avoided adding the flag twice if it is already present in OPENDJ_JAVA_ARGS.
• Preserved compatibility with older JVMs by skipping the flag when java --enable-native-access=ALL-UNNAMED --version is not supported.

Why

Bouncy Castle FIPS loads native code through System.load. Recent Java releases warn about restricted native access and require explicit opt-in using --enable-native-access=ALL-UNNAMED for code running on the classpath / unnamed module.

Without this flag, OpenDJ startup can produce noisy warnings today, and future Java releases may block the operation unless native access is explicitly enabled.

Compatibility

The new argument is added only after a successful JVM feature probe. This keeps existing installations compatible with Java versions that do not recognize --enable-native-access.

Validation

Performed local validation for the Unix startup helper:

sh -n opendj-server-legacy/resource/bin/_script-util.sh
bash -n opendj-server-legacy/resource/bin/_script-util.sh

Also verified:

• --enable-native-access=ALL-UNNAMED is appended when the JVM supports it.
• The argument is not duplicated when already present in OPENDJ_JAVA_ARGS.
• The argument is not appended when a JVM does not support it.

IDE inspection reported no new errors in the modified Windows batch file. Existing shellcheck-style warnings in _script-util.sh are unrelated to this change.