[chore]: Improved metrics_core test and remove duplicate patterns

[yelodevopsi]

• Bugfix: removed duplicate paths_* and hls_muxers_* patterns
• Rewrite regexp to pattern array instead:
  ** This gives specific error to which line fails in test32 and test64.
• The old code just tells "something" in the regexp is wrong, but not which

[aler9]

Hello, this is nice but there are a couple of missing things:

• the new test does not check for the presence of additional lines other than the ones defined inside patterns. For instance, if there's a extraneous metric called webrtc_should_not_be_here, the test allows it (while it shouldn't)
• the new test does not check for the presence of repeated lines - for instance, if there are two metrics srt_conns_mbps_send_rate and srt_conns_mbps_send_rate, the test allows it (while it shouldn't)

can you upgrade the code in order to account for these missing test cases?