Update IInputBuffer

[jamescourtney]

Expose Span methods on IInputBuffer via new IInputBuffer2 interface.

[codecov]

Codecov Report

Merging #267 (f268f62) into main (074b4d5) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #267      +/-   ##
==========================================
+ Coverage   95.67%   95.69%   +0.02%     
==========================================
  Files         119      119              
  Lines        7633     7674      +41     
  Branches      705      707       +2     
==========================================
+ Hits         7303     7344      +41     
  Misses        230      230              
  Partials      100      100              

Impacted Files	Coverage Δ
...rc/FlatSharp.Runtime/GeneratedSerializerWrapper.cs	82.83% <100.00%> (ø)
src/FlatSharp.Runtime/IO/ArrayInputBuffer.cs	100.00% <100.00%> (ø)
...rc/FlatSharp.Runtime/IO/ArraySegmentInputBuffer.cs	100.00% <100.00%> (ø)
src/FlatSharp.Runtime/IO/InputBufferExtensions.cs	96.66% <100.00%> (+1.01%)	⬆️
src/FlatSharp.Runtime/IO/MemoryInputBuffer.cs	100.00% <100.00%> (ø)
.../FlatSharp.Runtime/IO/ReadOnlyMemoryInputBuffer.cs	100.00% <100.00%> (ø)
src/FlatSharp.Runtime/Vectors/FlatBufferVector.cs	96.77% <100.00%> (+0.10%)	⬆️
...tSharp/Serialization/DeserializeClassDefinition.cs	100.00% <100.00%> (ø)
src/FlatSharp/TypeModel/ValueStructTypeModel.cs	97.61% <100.00%> (ø)

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