Avoid using String constructor on Vector{UInt8}

[nhz2]

The String constructor doesn't behave consistently for all AbstractVector{UInt8}. Normally it makes a copy, except for Vector{UInt8} where it truncates the input. In Julia this can in some weird cases lead to undefined behavior. Ref: JuliaLang/julia#54372 JuliaLang/julia#54424

This PR avoids potential issues with String(v::Vector{UInt8}) by using an internal copy_string(v::AbstractVector{UInt8}) function that should always make a copy of the input.

# version of String(v::AbstractVector{UInt8}) that works consistently.
function copy_string(v::AbstractVector{UInt8})::String
    String(v)
end
function copy_string(v::Vector{UInt8})::String
    GC.@preserve v unsafe_string(pointer(v), length(v))
end

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.61%. Comparing base (e550feb) to head (f632847).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #52   +/-   ##
=======================================
  Coverage   99.61%   99.61%           
=======================================
  Files           6        6           
  Lines         772      776    +4     
=======================================
+ Hits          769      773    +4     
  Misses          3        3           

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