RFR: 8373661: Add edge case tests for Objects.requireNonNull methods

[eunbin son]

## Summary
Adds comprehensive edge case tests for `Objects.requireNonNull`, 
`requireNonNullElse`, and `requireNonNullElseGet` methods to improve 
test coverage.

## Problem
The current test suite for `Objects.requireNonNull` methods covers 
basic cases but lacks edge case coverage.

## Solution
This PR adds tests for the following edge cases:
- requireNonNull with null Supplier parameter
- requireNonNull with Supplier that throws exception
- requireNonNullElse with both arguments null
- requireNonNullElseGet with null supplier
- requireNonNullElseGet with supplier returning null

## Issue
Fixes JDK-8373661

**JBS Issue Link**: https://bugs.java.com/bugdatabase/view_bug?bug_id=JDK-8373661

## Type of Change
- [x] Test addition/modification
- [ ] Bug fix
- [ ] New feature
- [ ] Documentation improvement
- [ ] Refactoring

## Testing

make test TEST="jtreg:test/jdk/java/util/Objects"

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Commit messages:
 - 8373661: Add edge case tests for Objects.requireNonNull methods

Changes: https://git.openjdk.org/jdk/pull/28845/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28845&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373661
  Stats: 126 lines in 1 file changed: 126 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28845.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28845/head:pull/28845

PR: https://git.openjdk.org/jdk/pull/28845