fix(plugin-vite): correct module resolution when Vite optimizeDeps is enabled (#3895)

[mryall-mawson]

Enabling optimizeDeps in Vite config causes the Fresh dev server to fail with file-not-found errors. In this mode, modules URLs include a query string which is not stripped before being passed to Deno's loader, which interprets them as filenames.

See #3895 for the full bug description and reproduction.

This PR provides a simple test case using an existing fixture, and the fix in plugin-vite to strip the query strings before loading.

Note there are some existing test failures on main which this PR does not attempt to fix.

[mryall-mawson]

I made a couple more fixes in this PR to get Vite’s optimizeDeps fully working in Fresh for client-side modules, with new tests to reproduce the issues I found along the way.

It is now tested and working for me, and I've released a fork here which we will use until this fix is released: https://jsr.io/@mawson/fresh-plugin-vite

We saw a reduction in our functional test execution time from 3.5 min to 2.5 mins against a dev server with optimizeDeps enabled for some large and deep dependency trees.

Edit: the specific error I saw was: Cannot read properties of undefined (reading '__$f') This indicated a duplicate copy of Preact was loaded on the front-end.