RFR: 8350041: Make libstringPlatformChars support static JDK [v3]

[Jiangli Zhou]

> Please review the fix to make `java/lang/String/nativeEncoding/StringPlatformChars.java` jtreg test: 
> 
> - Lookup `JNU_GetStringPlatformChars`, `JNU_ClassString` and `JNU_NewStringPlatform` dynamically
> - Remove `#include "jni_util.h"` and don't link `libstringPlatformChars.so` with `libjava.so`
> - Link with `-ldl` explicitly
> 
> The test passed on Linux, macos and Windows in GHA testing, https://github.com/jianglizhou/jdk/actions/runs/13320840902/job/37206171224

Jiangli Zhou has updated the pull request incrementally with one additional commit since the last revision:

  Update copyright year.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23646/files
  - new: https://git.openjdk.org/jdk/pull/23646/files/1de95b89..1a51b701

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23646&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23646&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23646.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23646/head:pull/23646

PR: https://git.openjdk.org/jdk/pull/23646