Update the set-output command (deprecation warning)

[jsoref]

Originally filed in actions/upload-artifact#351
https://github.com/actions/toolkit/blob/b00a9fd033f4b30f2355acd212f531ecbbb9b38f/packages/core/src/core.ts

Describe the bug
The set-output command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

To Reproduce
Steps to reproduce the behavior:
What would you like to be added?
- name: Upload Artifacts
uses: actions/upload-artifact@v3
When using this Action in a Workflow, GitHub displays a warning:

The set-output command is deprecated and will be disabled soon.

Expected behavior
No warnings.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.

[mrienstra]

Closed by #1178
Released in @actions/core 1.10.0