Remove 32-bit architectures from build scripts and support code

[faec]

Some Beats cross-builds are failing because we're still unintentionally packaging 32-bit builds, which haven't been supported since 8.0. This removes all live mentions in the build scripts and code to linux/386, windows/386, and darwin/386 architectures.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

[elasticmachine]

Pinging @elastic/elastic-agent (Team:Elastic-Agent)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2023-06-15T19:37:27.383+0000

• Duration: 81 min 30 sec

Test stats 🧪

Test	Results
Failed	0
Passed	27358
Skipped	2013
Total	29371

💚 Flaky test report

Tests succeeded.

🤖 GitHub comments

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