app/promauto: implement reset gauge

[corverroos]

Implement a ResetGauge to simplify "resetting of previously set labels".

category: misc
ticket: #2277

[gsora]

@corverroos CI is red because the metrics docs hasn't been updated, approved regardless because it looks fine otherwise

[codecov]

Codecov Report

Patch coverage: 53.33% and project coverage change: +0.15 🎉

Comparison is base (ee11d1e) 53.67% compared to head (061a8af) 53.83%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2289      +/-   ##
==========================================
+ Coverage   53.67%   53.83%   +0.15%     
==========================================
  Files         190      191       +1     
  Lines       25628    25658      +30     
==========================================
+ Hits        13757    13814      +57     
+ Misses      10188    10161      -27     
  Partials     1683     1683              

Impacted Files	Coverage Δ
app/monitoringapi.go	50.57% <0.00%> (-0.59%)	⬇️
p2p/metrics.go	0.00% <ø> (ø)
p2p/p2p.go	20.52% <0.00%> (-0.24%)	⬇️
app/promauto/resetgauge.go	91.30% <91.30%> (ø)
app/peerinfo/peerinfo.go	68.70% <100.00%> (-3.22%)	⬇️
core/scheduler/metrics.go	82.35% <100.00%> (+1.10%)	⬆️

... and 6 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.