fix(vite): fall back to file matching when resolved file does not exist in nx-vite-ts-paths plugin (#29472)

The fallback path resolution was only happening if the resolvedFile was
a falsy value, so it was returning inexistent filepaths.

This pull request includes a small but important change to the
`packages/vite/plugins/nx-tsconfig-paths.plugin.ts` file. The change
improves the reliability of resolving file paths by checking if the
resolved path exists before proceeding with fallback file matching.

*
[`packages/vite/plugins/nx-tsconfig-paths.plugin.ts`](diffhunk://#diff-ad026b24ed45d9df484cabc7e277fc9b4d7759560af36bf357cbc4186725ae0bL174-R176):
Added a check to verify if the resolved file path exists before using
fallback file matching.
* 
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## Current Behavior
<!-- This is the behavior we have today -->
The resolver doesn't resolve the full file path, it ignores the file
extension. For example, for a path like this:
`import mergeClassNames from '@projects/global/utils/mergeClassNames'`

It resolves to 
`absolutePath.../projects/libs/global/src/utils/mergeClassNames`

When vite is building a project, it doesn't find the file and it errors.

This happens because the resolved file path is not a falsy value, thus,
it doesn't run the fallback file path matching.

## Expected Behavior
<!-- This is the behavior we should expect with the changes in this PR
-->
What is expected is that it resolves to (notice the file extension)
`absolutePath.../projects/libs/global/src/utils/mergeClassNames.ts`

## Related Issue(s)
<!-- Please link the issue being fixed so it gets closed when this is
merged. -->

---------

Co-authored-by: Leosvel Pérez Espinosa <[email protected]>

Author: estebanfelipep

packages/vite/plugins/nx-tsconfig-paths.plugin.ts

@@ -171,7 +171,7 @@ There should at least be a tsconfig.base.json or tsconfig.json in the root of th
         resolvedFile = matchTsPathFallback?.(importPath);
       }
 
-      if (!resolvedFile) {
+      if (!resolvedFile || !existsSync(resolvedFile)) {
         if (tsConfigPathsEsm || tsConfigPathsFallback) {
           logIt(
             `Unable to resolve ${importPath} with tsconfig paths. Using fallback file matching.`