RFR: 8372978: [VectorAPI] Fix incorrect identity values in UMIN/UMAX reductions [v5]

[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.

Eric Fang has updated the pull request incrementally with one additional commit since the last revision:

  wrap the test loop within a try/catch to speed up the tests

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/28692/files
  - new: https://git.openjdk.org/jdk/pull/28692/files/b5237a28..e0e3d865

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28692&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28692&range=03-04

  Stats: 2457 lines in 33 files changed: 1638 ins; 273 del; 546 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