RFR: 8372978: [VectorAPI] Fix incorrect identity values in UMIN/UMAX reductions

[Eric Fang]

The original implementation of UMIN/UMAX reductions in JDK-8346174 used incorrect identity values in the Java implementation and test code.

Problem:
--------
UMIN was using MAX_OR_INF (signed maximum value) as the identity:
  - Byte.MAX_VALUE (127) instead of max unsigned byte (255)
  - Short.MAX_VALUE (32767) instead of max unsigned short (65535)
  - Integer.MAX_VALUE instead of max unsigned int (-1)
  - Long.MAX_VALUE instead of max unsigned long (-1)

UMAX was using MIN_OR_INF (signed minimum value) as the identity:
  - Byte.MIN_VALUE (-128) instead of 0
  - Short.MIN_VALUE (-32768) instead of 0
  - Integer.MIN_VALUE instead of 0
  - Long.MIN_VALUE instead of 0

This caused incorrect result. For example:
  UMAX([42,42,...,42]) returned 128 instead of 42

Solution:
---------
Use correct unsigned identity values:
  - UMIN: ($type$)-1 (maximum unsigned value)
  - UMAX: ($type$)0 (minimum unsigned value)

Changes:
--------
- X-Vector.java.template: Fixed identity values in reductionOperations
- gen-template.sh: Fixed identity values for test code generation
- templates/Unit-header.template: Updated copyright year to 2025
- Regenerated all Vector classes and test files

Testing:
--------
All types (byte/short/int/long) now return correct results in both interpreter mode (-Xint) and compiled mode.

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Commit messages:
 - 8372978: [VectorAPI] Fix incorrect identity values in UMIN/UMAX reductions

Changes: https://git.openjdk.org/jdk/pull/28692/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28692&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372978
  Stats: 364 lines in 37 files changed: 0 ins; 0 del; 364 mod
  Patch: https://git.openjdk.org/jdk/pull/28692.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28692/head:pull/28692

PR: https://git.openjdk.org/jdk/pull/28692