Reduce similar ambiguities

[Tokazama]

This doesn't solve all the issues related to similar, but it handles problems directly in this package. NamedDims and Metadata still have issues upstream.

[codecov]

Codecov Report

Merging #68 (9693bb7) into master (5eacd21) will increase coverage by 2.40%.
The diff coverage is 58.62%.

@@            Coverage Diff             @@
##           master      #68      +/-   ##
==========================================
+ Coverage   65.25%   67.65%   +2.40%     
==========================================
  Files          27       29       +2     
  Lines        2029     2288     +259     
==========================================
+ Hits         1324     1548     +224     
- Misses        705      740      +35     

Impacted Files	Coverage Δ
src/AxisIndices.jl	40.00% <ø> (-5.57%)	⬇️
src/centered_axis.jl	59.42% <ø> (-0.58%)	⬇️
src/combine.jl	48.03% <ø> (+3.09%)	⬆️
src/named.jl	56.06% <ø> (+5.63%)	⬆️
src/padded_axis.jl	63.70% <0.00%> (+2.36%)	⬆️
src/identity_axis.jl	40.90% <25.00%> (-2.47%)	⬇️
src/similar.jl	35.84% <35.84%> (ø)
src/errors.jl	54.54% <50.00%> (-1.02%)	⬇️
src/axis.jl	62.89% <52.77%> (+1.90%)	⬆️
src/utils.jl	55.17% <55.17%> (ø)
... and 35 more

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