Add _show_data function to skip data loading during show

[felixcremer]

This is to make sure, that DiskArrays don't getindex into data during show.
I added a fallback to true so that for non-DiskArray datasets this would not change in behaviour.

I thought about using isdisk, but I wasn't sure, where I could add this check because we don't have isdisk available in DimensionalData and in the extension it is too late.

I also added a test, that checks that DiskArrays based DimArrays don't access the data.

[rafaqz]

can_show_data is a bit clearer

[felixcremer]

I applied your suggestions and fixed the show test.
Locally I get the following unrelated test failure n the "inference" testset:

julia> x = DimArray(randn(2, 3, 4), (X, Y, Z));

julia> foo(x) = maximum(x; dims=(1, 2))
foo (generic function with 1 method)

julia> @inferred foo(x)
ERROR: return type DimArray{Float64, 3, Tuple{X{DimensionalData.Dimensions.Lookups.NoLookup{Base.OneTo{Int64}}}, Y{DimensionalData.Dimensions.Lookups.NoLookup{Base.OneTo{Int64}}}, Z{DimensionalData.Dimensions.Lookups.NoLookup{Base.OneTo{Int64}}}}, Tuple{}, Array{Float64, 3}, DimensionalData.NoName, DimensionalData.Dimensions.Lookups.NoMetadata} does not match inferred return type DimArray{Float64, 3, D, Tuple{}, Array{Float64, 3}, DimensionalData.NoName, DimensionalData.Dimensions.Lookups.NoMetadata} where D<:Tuple
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:44
 [2] top-level scope
   @ REPL[30]:1

I also get this on DimensionalData 0.29.24

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.91%. Comparing base (6db30de) to head (527e653).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1130   +/-   ##
=======================================
  Coverage   86.90%   86.91%           
=======================================
  Files          55       55           
  Lines        5338     5341    +3     
=======================================
+ Hits         4639     4642    +3     
  Misses        699      699           

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[felixcremer]

The last commit was needed because the string before a multiple instance assignment fails now after JuliaLang/julia#59742. I don't see why we wanted to have a string there anyway so I converted it to proper comments.