Generate NT_PROCSTAT_{AUXV,VMMAP,PS_STRINGS} in FreeBSD coredumps

Generate NT_PROCSTAT_{AUXV,VMMAP,PS_STRINGS} in FreeBSD coredumps

gcore generates NT_AUXV and NT_FILE notes for Linux targets.  On
FreeBSD auxv is stored in a NT_PROCSTAT_AUXV section, virtual memory
mappings are stored in a NT_PROCSTAT_VMMAP, and both are prefixed with
the struct size.  In addition, store a NT_PROCSTAT_PS_STRINGS note
saving the initial location of the argv[] and environment[] arrays.

gdb/ChangeLog:

	PR gdb/23105
	* fbsd-nat.c (fbsd_nat_target::xfer_partial): Add support for
	TARGET_OBJECT_FREEBSD_VMMAP and TARGET_OBJECT_FREEBSD_PS_STRINGS.
	* fbsd-tdep.c (fbsd_make_note_desc): New.
	(fbsd_make_corefile_notes): Write NT_PROCSTAT_AUXV,
	NT_PROCSTAT_VMMAP and NT_PROCSTAT_PS_STRINGS notes.
	* target.h (enum target_object) Add FreeBSD-specific
	TARGET_OBJECT_FREEBSD_VMMAP and TARGET_OBJECT_FREEBSD_PS_STRINGS.