`/etc/hosts` may be used as a denylist for undesired hosts on some systems.
In such usage scenarios the file may be large in size and parsing it may severely
impact shell startup time.
For example, on a system with `/etc/hosts` from https://github.com/StevenBlack/hosts:
```
% cat profile.zsh
#!/usr/bin/env zsh
zmodload zsh/zprof
source ./etc/zsh/zshrc
zprof
```
```
% ./profile.zsh | head -3
num calls time self name
-----------------------------------------------------------------------------------
1) 1 1181.93 1181.93 87.91% 1181.14 1181.14 87.85% grmlcomp
```
```
% NOETCHOSTS=1 ./profile.zsh | head -3
num calls time self name
-----------------------------------------------------------------------------------
1) 2 79.77 39.88 47.37% 79.77 39.88 47.37% compaudit
```
Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>