Bluetooth: Audio: Shell: Fix metadata argument

The metadata in the presets are just defined
using the BT_AUDIO_LC3_PRESET which ultimately
uses BT_CODEC_LC3_CONFIG_META which correctly
sets the data pointer, but the `value` array is unused.

So we cannot just update the `value`, as that is actually
not used in those cases, and the `data` pointer is `const`.

The solution is to a copy of the metadata data, and use
the copy when calling the API.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>