Convert metrics_table.py to a module

[jsoref]

Short description

This was identified by https://github.com/check-spelling-sandbox/pdns/security/quality/rules/py%2Fineffectual-statement
Fix suggested by dwfreed (who is not an AI, at least to my knowledge)

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document, including the AI Policy, and added a "Signed-off-by" to my commits
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• checked that this code was merged to master

[miodvallat]

Ah, but dwfreed is an AI: an Anonymous IRCer.

[coveralls]

Pull Request Test Coverage Report for Build 19308212842

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 6744 unchanged lines in 83 files lost coverage.
• Overall coverage decreased (-0.001%) to 73.034%

---

Files with Coverage Reduction	New Missed Lines	%
pdns/dnsdistdist/dnsdist-tcp.cc	1	76.95%
pdns/recursordist/rec-rust-lib/rust/src/bridge.hh	1	0.0%
pdns/recursordist/sortlist.hh	1	75.0%
modules/lmdbbackend/lmdbbackend.cc	2	72.81%
modules/pipebackend/pipebackend.cc	2	60.79%
pdns/dnsdistdist/dnsdist.cc	2	70.97%
pdns/dnsname.hh	2	92.95%
pdns/dnstap.cc	2	72.73%
pdns/recursordist/secpoll-recursor.cc	2	52.81%
pdns/sstuff.hh	2	62.02%

Totals
Change from base Build 19300033906:	-0.001%
Covered Lines:	127710
Relevant Lines:	164157

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💛 - Coveralls