cleanup(metrics): remove duplicated new_metric method

[Molter73]

What type of PR is this?

/kind cleanup

Any specific area of the project related to this PR?

/area libsinsp

Does this PR require a change in the driver versions?

What this PR does / why we need it:

This change was meant to go in as part of #1920, but somehow got lost in translation. Compilation of Falco will be fixed by falcosecurity/falco#3265.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[Molter73]

/cc @incertum @FedeDP

[github-actions]

Perf diff from master - unit tests

     4.34%     -1.57%  [.] sinsp_evt::load_params
     5.64%     +1.40%  [.] sinsp::next
    10.28%     +0.96%  [.] sinsp_parser::reset
     0.51%     +0.77%  [.] sinsp_evt::get_direction
     5.81%     -0.70%  [.] sinsp_evt::get_type
     5.22%     -0.52%  [.] next
     0.51%     +0.50%  [.] sinsp_filter_check::parse_field_name
     1.74%     -0.49%  [.] libsinsp::sinsp_suppress::process_event
     3.05%     +0.46%  [.] sinsp_thread_manager::get_thread_ref
     1.13%     +0.44%  [.] sinsp::fetch_next_event

Perf diff from master - scap file

    21.12%     -8.95%  [.] sinsp_filter_check::extract_nocache
     8.39%     +7.84%  [.] sinsp_filter_check::tostring
     4.24%     +6.52%  [.] sinsp_filter_check::rawval_to_string
    21.09%     -5.53%  [.] sinsp_evt_formatter::tostring_withformat
     3.70%     +3.52%  [.] std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_construct<char*>
     4.14%     +3.06%  [.] sinsp_filter_check::apply_transformers
     4.21%     +3.03%  [.] sinsp::next
     8.52%     +2.60%  [.] next
     8.37%     -2.54%  [.] sinsp_parser::reset
     8.24%     -2.46%  [.] sinsp_filter_check_event::extract_single

Heap diff from master - unit tests

peak heap memory consumption: 0B
peak RSS (including heaptrack overhead): 0B
total memory leaked: 0B

Heap diff from master - scap file

peak heap memory consumption: 0B
peak RSS (including heaptrack overhead): 0B
total memory leaked: 0B

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 50.99%. Comparing base (d22f7a4) to head (ae2d606).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1991   +/-   ##
=======================================
  Coverage   50.98%   50.99%           
=======================================
  Files         310      310           
  Lines       39612    39607    -5     
  Branches    17380    17313   -67     
=======================================
  Hits        20198    20198           
+ Misses      14342    14323   -19     
- Partials     5072     5086   +14     

☔ View full report in Codecov by Sentry.
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[poiana]

LGTM label has been added.

Git tree hash: 4c9f35d55723c9803d1f8152387598dfd10301e2

[FedeDP]

/milestone 0.18.0

[FedeDP]

/approve

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: FedeDP, Molter73

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