scripts/gdb: add 'lx-stack_depot_lookup' command.

scripts/gdb: add 'lx-stack_depot_lookup' command.

This command allows users to quickly retrieve a stacktrace using a handle
obtained from a memory coredump.

Example output:
(gdb) lx-stack_depot_lookup 0x00c80300
   0xffff8000807965b4 <kmem_cache_alloc_noprof+660>:    mov     x20, x0
   0xffff800081a077d8 <kmem_cache_oob_alloc+76>:        mov     x1, x0
   0xffff800081a079a0 <test_version_show+100>:  cbnz    w0, 0xffff800081a07968 <test_version_show+44>
   0xffff800082f4a3fc <kobj_attr_show+60>:      ldr     x19, [sp, #16]
   0xffff800080a0fb34 <sysfs_kf_seq_show+460>:  ldp     x3, x4, [sp, #96]
   0xffff800080a0a550 <kernfs_seq_show+296>:    ldp     x19, x20, [sp, #16]
   0xffff8000808e7b40 <seq_read_iter+836>:      mov     w5, w0
   0xffff800080a0b8ac <kernfs_fop_read_iter+804>:       mov     x23, x0
   0xffff800080914a48 <copy_splice_read+972>:   mov     x6, x0
   0xffff8000809151c4 <do_splice_read+348>:     ldr     x21, [sp, #32]

Link: https://lkml.kernel.org/r/20240723064902.124154-5-kuan-ying.lee@canonical.com
Signed-off-by: Kuan-Ying Lee <kuan-ying.lee@canonical.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>