logs: fix logs.disabled on Windows (#17199)

On Windows the executor returns an error when trying to open the `NUL` device
when we pass it `os.DevNull` for the stdout/stderr paths. Instead of opening the
device, use the discard pipe so that we have platform-specific behavior from the
executor itself.

Fixes: #17148

.changelog/17199.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+logs: Fixed a bug where disabling log collection would prevent Windows tasks from starting
+```

drivers/shared/executor/executor.go

@@ -181,7 +181,7 @@ func (nopCloser) Close() error { return nil }
 // Stdout returns a writer for the configured file descriptor
 func (c *ExecCommand) Stdout() (io.WriteCloser, error) {
 	if c.stdout == nil {
-		if c.StdoutPath != "" {
+		if c.StdoutPath != "" && c.StdoutPath != os.DevNull {
 			f, err := fifo.OpenWriter(c.StdoutPath)
 			if err != nil {
 				return nil, fmt.Errorf("failed to create stdout: %v", err)
@@ -197,7 +197,7 @@ func (c *ExecCommand) Stdout() (io.WriteCloser, error) {
 // Stderr returns a writer for the configured file descriptor
 func (c *ExecCommand) Stderr() (io.WriteCloser, error) {
 	if c.stderr == nil {
-		if c.StderrPath != "" {
+		if c.StderrPath != "" && c.StderrPath != os.DevNull {
 			f, err := fifo.OpenWriter(c.StderrPath)
 			if err != nil {
 				return nil, fmt.Errorf("failed to create stderr: %v", err)