Update GitHub Actions for set-output deprecation

[RytoEX]

Description

GitHub Actions has deprecated set-output. Replace usages of set-output in stdout with the new syntax to save the output to the new environment variable.

See: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

Motivation and Context

Don't want deprecation warnings hiding real issues.

How Has This Been Tested?

It hasn't. This was written by following documentation. A CI run will be the test.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Tweak (non-breaking change to improve existing functionality)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [ ] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.