Bump @actions/cache to 5.1.0, log cache write denied

[jasongin]

Description:

• Bump @actions/cache to v5.1.0 to pick up actions/toolkit#2435 Handle cache write error due to read-only token
• Update generated JavaScript files under dist
• Update license files for dependencies
• Bump minor version in package.json from 6.2.0 to 6.3.0

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

[Copilot]

Pull request overview

This pull request updates the action’s caching dependency (@actions/cache) to pick up improved handling/logging for cache write denials (e.g., read-only tokens), and aligns the action’s own cache-save logging and published artifacts with that behavior.

Changes:

• Bump @actions/cache to ^5.1.0 and bump action version to 6.3.0.
• Add a debug log when saveCache returns -1 (cache not saved) to avoid redundant warnings while still providing traceability.
• Update generated dist/** bundles and dependency license metadata to reflect the dependency update.

Show a summary per file

File	Description
src/cache-save.ts	Adds debug logging when cache save returns -1 (not saved).
package.json	Bumps action version to 6.3.0 and @actions/cache to ^5.1.0.
package-lock.json	Updates lockfile entries for the version bump and cache dependency.
dist/setup/index.js	Updates bundled @actions/cache code to include cache write denied handling.
dist/cache-save/index.js	Updates bundled output, including the new -1 debug log and cache write denied handling.
.licenses/npm/@actions/cache.dep.yml	Updates dependency license metadata for @actions/cache 5.1.0.

Copilot's findings

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• Files reviewed: 3/6 changed files
• Comments generated: 2

[jasongin]

The e2e-cache and Validate PyPy e2e workflows are unrelated to this PR; they are failing on main branch also. It looks like they're fixed by #1322.