Fix test retry cleanup (#43011)

As noticed in
#42966 (review)
we weren't resetting tests correctly on retry causing an incorrect pass.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have a helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the
feature request has been accepted for implementation before opening a
PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have a helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm build && pnpm lint`
- [ ] The "examples guidelines" are followed from [our contributing
doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)

run-tests.js

@@ -356,7 +356,13 @@ async function main() {
         } catch (err) {
           if (i < numRetries) {
             try {
-              const testDir = path.dirname(path.join(__dirname, test))
+              let testDir = path.dirname(path.join(__dirname, test))
+
+              // if test is nested in a test folder traverse up a dir to ensure
+              // we clean up relevant test files
+              if (testDir.endsWith('/test') || testDir.endsWith('\\test')) {
+                testDir = path.join(testDir, '../')
+              }
               console.log('Cleaning test files at', testDir)
               await exec(`git clean -fdx "${testDir}"`)
               await exec(`git checkout "${testDir}"`)