refactor(core): use has instead of get to test for existence in ExecEnv

[Josh-Cena]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

This is better because the has check may be proxified differently from a get check. We should always use has for existence.

Test Plan

Test links

Deploy preview: https://deploy-preview-_____--docusaurus-2.netlify.app/

Related issues/PRs

[netlify]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 73	🟢 100	🟢 100	🟢 100	🟢 90	Report
/docs/installation	🟠 83	🟢 100	🟢 100	🟢 100	🟢 90	Report

[github-actions]

Size Change: +10 B (0%)

Total Size: 805 kB

ℹ️ View Unchanged

Filename	Size	Change
website/.docusaurus/globalData.json	52.6 kB	0 B
website/build/assets/css/styles.********.css	106 kB	0 B
website/build/assets/js/main.********.js	607 kB	+10 B (0%)
website/build/index.html	38.9 kB	0 B

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