refactor(router-vite-plugin): remove the start logic from @tanstack/router-vite-plugin and update @tanstack/start with the new imports

[SeanCassiere]

Following #1768, this PR removed the Start logic from @tanstack/router-vite-plugin and updates the @tanstack/start package to use @tanstack/start-vite-plugin.

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✅ Successfully ran 4 targets

• nx run-many --target=test:e2e:replay
• nx affected --targets=test:format,test:eslint,test:unit,test:build,build --parallel=3
• nx affected --target=test:types --exclude=examples/**
• nx affected --target=build --exclude=examples/**

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