[chore] Make TestReadRotatingFiles more robust on Windows (open-telem…

…etry#36032)

Make the remove operation an "eventually required" since on Windows you
can't delete if there are still handles opened to the file. This should
prevent failures like
https://github.com/open-telemetry/opentelemetry-collector-contrib/actions/runs/11559461472/job/32174166127#step:8:259
see below.

On my box multiple runs were failing but that higher frequency of
failures was probably to the usage of antivirus software, this change
made it to pass consistently on my box.

```terminal
D:/a/opentelemetry-collector-contrib/opentelemetry-collector-contrib/.tools/gotestsum --rerun-fails=1 --packages="./..." -- -race -timeout 600s -parallel 4 --tags=""
✖  . (1.777s)

=== Failed
=== FAIL: . TestReadRotatingFiles/CopyTruncate (2.73s)
    filelog_test.go:194: 
        	Error Trace:	D:/a/opentelemetry-collector-contrib/opentelemetry-collector-contrib/receiver/filelogreceiver/filelog_test.go:194
        	Error:      	Received unexpected error:
        	            	remove C:\Users\RUNNER~1\AppData\Local\Temp\TestReadRotatingFilesCopyTruncate3537600095\001\test-backup.log: The process cannot access the file because it is being used by another process.
        	Test:       	TestReadRotatingFiles/CopyTruncate

=== FAIL: . TestReadRotatingFiles (0.00s)

=== FAIL: . TestReadRotatingFiles/CopyTruncate (re-run 1) (1.63s)
    filelog_test.go:194: 
        	Error Trace:	D:/a/opentelemetry-collector-contrib/opentelemetry-collector-contrib/receiver/filelogreceiver/filelog_test.go:194
        	Error:      	Received unexpected error:
        	            	remove C:\Users\RUNNER~1\AppData\Local\Temp\TestReadRotatingFilesCopyTruncate134417[272](https://github.com/open-telemetry/opentelemetry-collector-contrib/actions/runs/11559461472/job/32174166127#step:8:273)3\001\test-backup.log: The process cannot access the file because it is being used by another process.
        	Test:       	TestReadRotatingFiles/CopyTruncate

=== FAIL: . TestReadRotatingFiles (re-run 1) (0.00s)
```

receiver/filelogreceiver/filelog_test.go

@@ -5,6 +5,7 @@ package filelogreceiver
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -190,9 +191,13 @@ func (rt *rotationTest) Run(t *testing.T) {
 			if rt.copyTruncate {
 				// Recreate the backup file
 				// if backupFileName exists
-				if _, err = os.Stat(backupFileName); err == nil {
-					require.NoError(t, os.Remove(backupFileName))
-				}
+				require.Eventually(t, func() bool {
+					// On Windows you can't remove a file if it still has some handle opened to it. So remove the file
+					// in a loop until any async operation on it is done.
+					removeErr := os.Remove(backupFileName)
+					return errors.Is(removeErr, os.ErrNotExist)
+				}, 5*time.Second, 100*time.Millisecond)
+
 				backupFile, openErr := os.OpenFile(backupFileName, os.O_CREATE|os.O_RDWR, 0600)
 				require.NoError(t, openErr)