fix(vite-dev-server): Use viteConfig.server.port if defined

[michaelhays]

• Closes [@cypress/vite-dev-server] Ability to select different port when running dev server #15892

User facing changelog

Allows the user to define a server port in their viteConfig when running the Vite dev server.

Additional details

Pretty simple/benign change -- let me know if I need to add tests or do anything else.

PR Tasks

• Have tests been added/updated?
• Has the original issue or this PR been tagged with a release in ZenHub?
• Has a PR for user-facing changes been opened in cypress-documentation?
• Have API changes been updated in the type definitions?
• Have new configuration options been added to the cypress.schema.json?

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[elevatebart]

Thanks @michaelhays good catch,
Your PR will help.