Make subsys API/descriptor structs static const to save RAM

[Copilot]

API callback structures and USB/DAP descriptors in subsys/ are defined as mutable globals despite containing only function pointers and constant configuration data that never change at runtime.

Changes

Modified 30 files to add static const to 36 struct definitions:

USB device classes (9 files)

• usbd_class_api structs: mctp_usb, msc, dfu, uac2, hid, loopback, cdc_acm, tracing
• USB descriptors: dfu_mode_desc, string_descr, func_desc

Backend APIs (8 files)

• Coredump: logging, in_memory, intel_adsp_mem_window, flash_partition
• Logging multidomain: log_backend_ipc_service, log_link_ipc_service, log_multidomain_link
• DAP: dap_func_api + descriptor macro

Bluetooth (8 files)

• Audio: ascs_iso_ops, broadcast_sink_iso_ops, unicast_client_iso_ops, broadcast_source_iso_ops, bap_stream_ops
• Classic: goep_rfcomm_ops, bip_rfcomm_ops, bip_l2cap_ops, tg/ct_bip_transport_ops

Other subsystems (5 files)

• Settings: settings_nvs_itf, settings_zms_itf
• Filesystem: ffa_op_callbacks
• Emul: ap_emul_api
• Network L2: any_api

// Before
struct usbd_class_api mctp_usb_class_api = {
    .request = mctp_usb_class_request,
    .enable = mctp_usb_class_enable,
};

// After
static const struct usbd_class_api mctp_usb_class_api = {
    .request = mctp_usb_class_request,
    .enable = mctp_usb_class_enable,
};

Excluded

Structures with runtime-mutable fields were intentionally not changed:

• Network packet filter rules (sys_slist nodes, locks)
• SMP transport (k_work, k_fifo)
• MCUmgr group registrations (list nodes)

Original prompt

in subsys code, look for all structs that should be static const to save ram

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