Raspberry Pi Pico multicore - Arduino tone library does not work in Core1

****
The Arduino tone library works in Core0 but it does not work in Core1. All you get is an initial "blip" sound and that's it.

Test Code based on the Arduino melody example (to get pitches.h go to the melody example in IDE):

```
#include
#include "pico/multicore.h"
#include "pitches.h"

// notes in the melody:
int melody[] = {NOTE_C4, NOTE_G3, NOTE_G3, NOTE_A3, NOTE_G3, 0, NOTE_B3, NOTE_C4};

// note durations: 4 = quarter note, 8 = eighth note, etc.:
int noteDurations[] = { 4, 8, 8, 4, 4, 4, 4, 4 };

void core1_entry() {

// iterate over the notes of the melody:
for (int thisNote = 0; thisNote < 8; thisNote++) {

// to calculate the note duration, take one second divided by the note type.
//e.g. quarter note = 1000 / 4, eighth note = 1000/8, etc.
int noteDuration = 1000 / noteDurations[thisNote];
tone(18, melody[thisNote], noteDuration);

// to distinguish the notes, set a minimum time between them.
// the note's duration + 30% seems to work well:
int pauseBetweenNotes = noteDuration * 1.30;
uint32_t t_now = millis();
while ((millis() - t_now) < (pauseBetweenNotes));
// stop the tone playing:
noTone(18);
}
}

void setup() {
multicore_launch_core1(core1_entry);
}

void loop() {
sleep_ms(2000);
}

```

Start by reproducing the provided sketch, focusing on core1_entry and the tone()/noTone() calls after multicore_launch_core1. Trace the Arduino tone behavior on Core1 and compare it with Core0; done means the melody plays fully on Core1 rather than producing only an initial blip.

Written by the indexing model from the issue text.