refactor(runtime): seal ES module namespace object instead of feezing

[sheremet-va]

Description

According to MDN ES modules are actually sealed and not frozen. This doesn't make any difference in the Vite case because we define getters so redefining properties always throws an error anyway.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines, especially the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Update the corresponding documentation if needed.
• Ideally, include relevant tests that fail without this PR but pass with it.

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