fix(glob): server perf when globbing huge dirs

[tony19]

The vite:import-glob plugin was unnecessarily watching globbed files (and doing so without checking for duplicates). This causes significant overhead when the file list is large (2K or more). It's also redundant to watch the files because createServer() already recursively watches the project's root directory.

fixes #9391

Description

Additional context

I'd submit a unit test for this, but not yet sure how. The test-serve command is flaky on my machine (even without any of my changes).

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[antfu]

I guess that makes sense. If a globbed file been imported, it should already been aware by the dev server so yeah probably this is redundant.