…ml settings for webserver.paths.webroot and webserver.paths.webhome

What does this PR aim to accomplish?:

Attempt to address #5980

How does this PR accomplish the above?:

Update advanced/Scripts/update.sh to source utils.sh and build the ADMIN_INTERFACE_DIR variable from configuration in pihole.toml via the getFTLConfigValue() function. Also change a hard coded reference of /var/www/html/admin in output string to use the ADMIN_INTERFACE_DIR variable.

Update advanced/Scripts/updatecheck.sh to build an ADMIN_INTERFACE_DIR variable from configuration in pihole.toml via the getFTLConfigValue() function and change hard coded references to /var/www/html/admin to use the added ADMIN_INTERFACE_DIR variable.

Update automated install/uninstall.sh to source utils.sh and to build an ADMIN_INTERFACE_DIR variable from configuration in pihole.toml via the getFTLConfigValue() function. Add a check that if web UI path is not the default of /var/www/html/admin do not automatically delete the custom path, but tell user to delete manually. This is a bit of a work around to deal with potentially "unsafe" paths getting pulled from pihole.toml (and its a custom config, so possibly a fair ask).

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