Make size(arr, tohighdimension) return 1

[felixcremer]

This makes size(zarr, dimnum= return 1 for to large dimensions numbers and give a better error message for negative dimension numbers.

This is needed so that concatenation of cubes backed by a Zarr array still work in DiskArrays after
JuliaIO/DiskArrays.jl#280

[coveralls]

Pull Request Test Coverage Report for Build 18913411990

Details

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.05%) to 89.338%

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Totals
Change from base Build 18793430184:	0.05%
Covered Lines:	972
Relevant Lines:	1088

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💛 - Coveralls

[felixcremer]

The nightly failures are an unrelated Pkg loading of precompiled packages problem and the codecov check is just strange. Because on codecov itself it looks as if all lines are hit.

[nhz2]

Looks good. Though a more basic error message without string interpolation might slightly improve performance.