Tweak CHAOS TXT local.api.ftl

[DL6ER]

What does this implement/fix?

Rather recently, #2233 changed the response to dig +short CHAOS TXT local.api.ftl from localhost as hard-coded host name to pi.hole. However, on systems which do not use FTL as their DNS resolver, the later does actually not resolve. The initial trigger for said change was #2192 where a user described that they cannot use the API because they configured their web server to NOT listen on 127.0.0.1 at all.

The PR revisits the initial issue altogether and, instead of using any fixed host name, gets the actual IPs the webserver was bound to and reports this, e.g.

$ sudo pihole-FTL --config webserver.port
80,[::]:80,443s,[::]:443s,127.0.0.67:445s

$ dig CHAOS TXT local.api.ftl +short
"http://127.0.0.1:80/api/" "http://[::1]:80/api/" "https://127.0.0.1:443/api/" "https://[::1]:443/api/" "https://127.0.0.67:445/api/"

For ports not specified with specific IP, CivetWeb binds to the wildcard address (0.0.0.0). We substitute this with 127.0.0.1 as not all clients behave well when 0.0.0.0 is passed to them.

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Related issue or feature (if applicable): Fixes #2192. Fixes #2252

Pull request in docs with documentation (if applicable): N/A

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2. I have commented my proposed changes within the code.
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Checklist:

• The code change is tested and works locally.
• I based my code and PRs against the repositories developmental branch.
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[DL6ER]

Also confirmed working by OP in #2192