analyze: add 'malloc' verb to dump malloc_info()

analyze: add 'malloc' verb to dump malloc_info()

Gets the memory state of the manager:

root@image:~# systemd-analyze malloc
<malloc version=1>
<heap nr=0>
<sizes>
  <size from=33 to=33 total=396 count=12/>
  <unsorted from=20385 to=20385 total=20385 count=1/>
</sizes>
<total type=fast count=0 size=0/>
<total type=rest count=14 size=36589/>
<system type=current size=1691648/>
<system type=max size=1839104/>
<aspace type=total size=1691648/>
<aspace type=mprotect size=1691648/>
</heap>
<total type=fast count=0 size=0/>
<total type=rest count=14 size=36589/>
<total type=mmap count=0 size=0/>
<system type=current size=1691648/>
<system type=max size=1839104/>
<aspace type=total size=1691648/>
<aspace type=mprotect size=1691648/>
</malloc>