DEBUG: pollers: add name hint for large memory areas used by pollers

DEBUG: pollers: add name hint for large memory areas used by pollers

Thanks to ("MINOR: tools: add vma_set_name() helper"), set a name hint
for large memory areas allocated by pollers upon init so that they can
be easily indentified in /proc/<pid>/maps.

For now, only linux-compatible pollers are considered since vma_set_name()
requires a recent linux kernel (>= 5.17).

Depending on malloc() implementation, such memory areas will normally be
merged on the heap under MMAP_THRESHOLD (128 kB by default) and will
have a dedicated memory area once the threshold is exceeded. As such, when
large enough, they will appear like this in /proc/<pid>/maps:

7ec6b2d40000-7ec6b2d61000 rw-p 00000000 00:00 0                          [anon:ev_poll:fd_evts_wr]
7ec6b2d61000-7ec6b2d82000 rw-p 00000000 00:00 0                          [anon:ev_poll:fd_evts_rd]