Improve focus distance precision for Nikon Z (backport #2739)

[mergify]

This is an automatic backport of pull request #2739 done by Mergify.

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[codecov]

Codecov Report

Merging #2742 (aa65c46) into 0.28.x (414bff1) will increase coverage by 0.00%.
Report is 44 commits behind head on 0.28.x.
The diff coverage is 40.00%.

@@           Coverage Diff           @@
##           0.28.x    #2742   +/-   ##
=======================================
  Coverage   63.92%   63.92%           
=======================================
  Files         103      103           
  Lines       22306    22320   +14     
  Branches    10796    10803    +7     
=======================================
+ Hits        14259    14269   +10     
- Misses       5827     5828    +1     
- Partials     2220     2223    +3     

Files Changed	Coverage Δ
include/exiv2/image.hpp	100.00% <ø> (ø)
include/exiv2/matroskavideo.hpp	60.00% <ø> (ø)
include/exiv2/slice.hpp	90.56% <ø> (ø)
include/exiv2/value.hpp	85.11% <ø> (ø)
src/basicio.cpp	50.52% <0.00%> (ø)
src/canonmn_int.cpp	72.88% <ø> (ø)
src/panasonicmn_int.cpp	52.58% <ø> (ø)
src/quicktimevideo.cpp	60.14% <0.00%> (ø)
src/rafimage.cpp	20.29% <ø> (ø)
src/riffvideo.cpp	62.18% <ø> (ø)
... and 13 more