Upgrade to Node20

[nonrational]

This PR updates cache-result-action to use Node 20. After this merges, I will tag the new commit as v2 and v2.0.0. We will then want to update our usage(s) in other repos to point to @v2.

From Github:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: parallel-markets/[email protected]. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

Node 16 has reached its end of life, prompting us to initiate its deprecation process for GitHub Actions. Our plan is to transition all actions to run on Node 20 by Spring 2024. We will actively monitor the migration's progress and gather community feedback before finalizing the transition date. Starting October 23rd, workflows containing actions running on Node 16 will display a warning to alert users about the upcoming migration.

[shortcut-integration]

This pull request has been linked to Shortcut Story #14167: cache-result-action - Upgrade nodejs version from 16 to 20.