Rename jdkFile input to jdk-file with deprecated alias support

[Copilot]

Description:
This updates setup-java input naming consistency by introducing jdk-file as the canonical input while preserving jdkFile as a backward-compatible alias. The alias now emits a deprecation warning only when it is the value actually used.

• Input contract

  • action.yml now defines jdk-file as the primary input.
  • jdkFile remains supported as a deprecated alias.

• Runtime behavior

  • Added centralized input resolution in getJdkFileInput().
  • Resolution order: prefer jdk-file; fall back to jdkFile.
  • Deprecation warning is emitted only when falling back to jdkFile.

• User-facing text and examples

  • Updated docs/workflow examples to use jdk-file.
  • Updated local installer missing-input error text to jdk-file.

• Test coverage

  • Added tests for:
    • canonical jdk-file input
    • alias fallback with warning
    • precedence (jdk-file over jdkFile) without warning

export function getJdkFileInput() {
  const jdkFile = core.getInput(INPUT_JDK_FILE);
  const deprecatedJdkFile = core.getInput(INPUT_JDK_FILE_DEPRECATED);

  if (!jdkFile && deprecatedJdkFile) {
    core.warning(
      "Input 'jdkFile' is deprecated and will be removed in a future release. Please use 'jdk-file' instead."
    );
  }

  return jdkFile || deprecatedJdkFile;
}

Related issue:

• Rename jdkFile property #1077

Check list:

• Ran npm run check locally (format, lint, build, test) and all checks pass.
• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

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