[jdk21u-dev] RFR: 8320570: NegativeArraySizeException decoding >1G UTF8 bytes with non-ascii characters

[Amos Shi]

Backport of [JDK-8320570](https://bugs.openjdk.org/browse/JDK-8320570)
- `NegativeSize.java` - Clean backport
- `String.java` - only 1 line change is unclean, the rest are clean. Details as bellow.
- This PR contains 2 commits
  - The commit 1: is a clean backport part
  - The commit 2: is a manual fix of the following 1 line:
    - In the `jdk master` branch, the variable name is `utf16`
	- Well in `jdk21u-dev`, the varialbe name is `buf`
	- So we manully applied the following line


@@ -592,7 +592,7 @@
                     this.coder = LATIN1;
                     return;
                 }
-                byte[] utf16 = new byte[length << 1];
+                byte[] utf16 = StringUTF16.newBytesFor(length);
                 StringLatin1.inflate(latin1, 0, utf16, 0, dp);
                 dp = decodeUTF8_UTF16(latin1, sp, length, utf16, dp, true);
                 if (dp != length) {



- So this PR can be considered as `semantics clean`


Testing
- Local: Passed on MacOS M1 laptop
  - `test/jdk/java/lang/String/CompactString/NegativeSize.java` - Test results: passed: 1
- Pipeline: 
- Testing Machine:

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

Commit messages:
 - Manual merge the line to jdk21u-dev
 - Backport 82796bdebbf56b98ec97a6d572ed68c2842f60c6

Changes: https://git.openjdk.org/jdk21u-dev/pull/344/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=344&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320570
  Stats: 82 lines in 2 files changed: 75 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/344.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/344/head:pull/344

PR: https://git.openjdk.org/jdk21u-dev/pull/344