Improve overflow error message

[kimikage]

This displays the fixed point type of the input in the message, not the rawtype. (cf. #190 (comment))

julia> checked_add(0.5N0f8, 0.5N0f8) # this PR
ERROR: OverflowError: 0.502N0f8 + 0.502N0f8 overflowed for type N0f8

Of course, more information could be added to the error message, but I think the error message in the constructor is sufficient to supplement it.

julia> 1.004N0f8
ERROR: ArgumentError: N0f8 is an 8-bit type representing 256 values from 0.0 to 1.0; cannot represent 1.004

This also avoids the stall with checked_{add/sub} on Windows. (cf. #190 (comment)) TBH, this is the real purpose of this PR. 😅

julia> @btime checked_add.($x, $y);
  898.900 μs (2 allocations: 976.70 KiB) # before (on Windows)
  577.699 μs (2 allocations: 976.70 KiB) # after (on Windows)
  678.800 μs (2 allocations: 976.70 KiB) # before (on Linux)
  679.500 μs (2 allocations: 976.70 KiB) # after (on Linux)

[kimikage]

I had excluded typemin and typemax with the intention of writing generic code for 100% testing. They have a risk of causing inconsistencies due to the rounding errors in floating point operations.
However, I decided against supporting non-8-bit types in 100% tests for multiplication. So we can safely include typemin and typemax for 8-bit types.

[codecov]

Codecov Report

Merging #214 into master will increase coverage by 0.23%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #214      +/-   ##
==========================================
+ Coverage   88.24%   88.48%   +0.23%     
==========================================
  Files           6        6              
  Lines         485      495      +10     
==========================================
+ Hits          428      438      +10     
  Misses         57       57              

Impacted Files	Coverage Δ
src/FixedPointNumbers.jl	85.14% <100.00%> (+0.90%)	⬆️

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