fix: call buildStart only once when using next port

[sapphi-red]

Description

This PR is a partial revert of #12593.

Because httpServer.listen will be called multiple times when falling back to another port, buildStart hook was called multiple times. This was making the object-hook playground test failing on my machine (this count was 4).

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.
• Read the Pull Request Guidelines and follow the PR Title Convention.
• 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).
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[bluwy]

Thanks! This make sense, I wasn't sure why it was needed before.

[dominikg]

this seems to break vite-plugin-svelte tests with hmr (testcase reload after svelte config change). https://github.com/vitejs/vite-ecosystem-ci/actions/runs/4550450699/jobs/8024503923

[dominikg]

ecosystem-ci bisect output

The first bad commit could be any of:
0f9ad6896ae93f79cc7ef6fbb2fd56047d719245
e10c6bdc757836781a9285ad2a6a3611bb9d6855
We cannot bisect more!
error while bisecting Error: Command failed with exit code 2: git bisect skip
There are only 'skip'ped commits left to test.
The first bad commit could be any of:
0f9ad6896ae93f79cc7ef6fbb2fd56047d719245
e10c6bdc757836781a9285ad2a6a3611bb9d6855