fix incorrect serialization of some concrete types

[neveritt]

This PR addresses #191.

Changes

• TheFixedSizeNumber or SignedNumber are now handled correctly in both readproto and writeprotoby converting based onattrib.ptyp`.
• To keep the speedup of Make wiretypes into julia types and specialize methods on these types #188, I converted attrib.ptyp to the corresponding Julia type.
• I added tests for a known value of concrete types (Int64, SignedNumber{Int64}...) and arrays of concrete types.

A minor fix of conversions of FixedSizeNumber and SignedNumber is also in this PR.

Notes

Note that the meta for dictionaries seem not to support FixedSizeNumber or SignedNumber

ProtoBuf.jl/src/codec.jl

Line 571 in 0428aee

function mapentry_meta(typ::Type{Dict{K,V}}) where {K,V}

due to mapentry_meta being called with the julia type as argument, and only use that to set ProtoMetaAttribs, an issue that predates the issue introduced in #188.
Because of that I have not added tests for maps but I tried to ensure that readproto and writeproto can handle those cases once ProtoMetaAttribs is set correctly.

[codecov]

Codecov Report

Merging #193 (7287f30) into master (0428aee) will increase coverage by 1.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #193      +/-   ##
==========================================
+ Coverage   67.95%   69.10%   +1.14%     
==========================================
  Files          19       19              
  Lines        2684     2690       +6     
==========================================
+ Hits         1824     1859      +35     
+ Misses        860      831      -29     

Impacted Files	Coverage Δ
src/codec.jl	94.80% <100.00%> (+6.70%)	⬆️

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