Allow pihole to access subdirs in /etc/pihole

[yubiuser]

What does this PR aim to accomplish?:

Before FTL starts we execute the pre-start script, which ensures that permissions are set correctly to various files and dirs.

pi-hole/advanced/Templates/pihole-FTL-prestart.sh

Lines 19 to 24 in 96640ea

	# Ensure that permissions are set so that pihole-FTL can edit all necessary files
	chown -R pihole:pihole /etc/pihole /var/log/pihole
	chmod -R 0640 /var/log/pihole
	chmod -R 0660 /etc/pihole
	# allow all users to enter the directories
	chmod 0755 /etc/pihole /var/log/pihole

However, we forgot to set the execution bit on the subdirs in /etc/pihole so FTL (running as pihole user) was not able to access the dirs , despite being the owner of the dirs. This resulted in errors on each FTL restart like

2023-10-13 08:58:14.547 [180M] WARNING: copy_file(): Failed to open "/etc/pihole/config_backups/pihole.toml.1" for writing: Permission denied
2023-10-13 08:58:14.547 [180M] WARNING: Rotation /etc/pihole/pihole.toml -(COPY)> /etc/pihole/config_backups/pihole.toml.1 failed
2023-10-13 08:58:14.547 [180M] INFO: Writing config file
2023-10-13 08:58:14.548 [180M] WARNING: copy_file(): Failed to open "/etc/pihole/config_backups/dnsmasq.conf.1" for writing: Permission denied
2023-10-13 08:58:14.548 [180M] WARNING: Rotation /etc/pihole/dnsmasq.conf -(COPY)> /etc/pihole/config_backups/dnsmasq.conf.1 failed
2023-10-13 08:58:14.548 [180M] WARNING: copy_file(): Failed to open "/etc/pihole/config_backups/custom.list.1" for writing: Permission denied
2023-10-13 08:58:14.548 [180M] WARNING: Rotation /etc/pihole/custom.list -(COPY)> /etc/pihole/config_backups/custom.list.1 failed

How does this PR accomplish the above?:

Set the execution bit on subdirs in /etc/pihole.

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[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/user-pihole-permissions-on-pihole-folders-are-not-writable/65443/12

[DL6ER]

We will finally get all the permissions right

[DL6ER]

That's some very interesting solution. I'd probably have done it on an individual basis but I do see how this will prevent us from forgetting to address this in the future 👍