include/debug.h: Use <nuttx/debug.h> in apps

[PiyushPatle26]

Note: Please adhere to Contributing Guidelines.

Summary

Update nuttx-apps to include <nuttx/debug.h> instead of <debug.h>.

This is the apps-side follow-up to the corresponding nuttx change that moves
the NuttX-specific debug header from include/debug.h to
include/nuttx/debug.h. Since debug.h is not a POSIX or standard C header,
using the namespaced path avoids collisions with external projects that may
also define a debug.h.

This change is mechanical: it updates existing include directives across
nuttx-apps to use the new header location.

Impact

• Aligns nuttx-apps with the new canonical debug header location in nuttx.
• Avoids continued dependency on the deprecated top-level <debug.h> path.
• No intended functional behavior change.
• No board-specific or hardware-specific impact.
• Keeps nuttx-apps compatible with the corresponding nuttx header move.

Testing

Validation performed on Ubuntu Linux.

Host:

• OS: Ubuntu Linux
• Repository: nuttx-apps

Verification:

• Verified there are no remaining source/header includes of <debug.h> in
  nuttx-apps after the update.
• This change is a include-path update only; no runtime behavior is
  intended to change.

Target:

• N/A for direct runtime testing in nuttx-apps alone

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