Makes the float-gauges lock-free

name                      old time/op  new time/op  delta
CounterFloat64Parallel-8  1.45µs ±10%  0.85µs ± 6%  -41.65%  (p=0.008 n=5+5)

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Co-authored-by: Exca-DK <dev@DESKTOP-RI45P4J.localdomain>
Co-authored-by: Martin Holst Swende <martin@swende.se>