refactor(hex): convert to class-based

[JamieMagee]

Changes:

Convert the hex datasource to be class-based.

This PR also adds caching for hex and I have some questions:

• Is this datasource safe to cache?
  • My research says yes, but I'd rather check with someone who knows more
• How long should it be cached for?
  • The default 30 minutes appears to be okay
• Is lookupName a sufficient key?
  • hex doesn't support custom registries, and there is only 1 default registry, so lookupName on its own should be enough

Context:

Part of #8647

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I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[renovate-release]

🎉 This PR is included in version 25.51.5 🎉

The release is available on:

• GitHub release
• 25.51.5

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